ACORN INVESTMENT TRUST, 497, 2000-10-05

ACORN INVESTMENT TRUST
497, 2000-10-05

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<PAGE>

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LIBERTY ACORN TRUST Prospectus, September 29, 2000
-------------------------------------------------------------

. LIBERTY ACORN FUND
. LIBERTY ACORN INTERNATIONAL
. LIBERTY ACORN USA
. LIBERTY ACORN TWENTY
. LIBERTY ACORN FOREIGN FORTY

Class Z Shares

Advised by Liberty Wanger Asset Management, L.P.

Only eligible investors may purchase Class Z shares. See "Your Account -Eligible
Investors" for more information.

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is accurate or complete.
Any representation to the contrary is a criminal offense.

<TABLE>
<CAPTION>
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TABLE OF CONTENTS
<S> <C>
LIBERTY ACORN FUND 2
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Investment Goal.................................................. 2
Principal Investment Strategies.................................. 2
Principal Investment Risks....................................... 2
Performance History.............................................. 5
Your Expenses.................................................... 6

LIBERTY ACORN INTERNATIONAL 7
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Investment Goal.................................................. 7
Principal Investment Strategies.................................. 7
Principal Investment Risks....................................... 7
Performance History.............................................. 10
Your Expenses.................................................... 11

LIBERTY ACORN USA 12
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Investment Goal.................................................. 12
Principal Investment Strategies.................................. 12
Principal Investment Risks....................................... 12
Performance History.............................................. 14
Your Expenses.................................................... 15

LIBERTY ACORN TWENTY 16
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Investment Goal.................................................. 16
Principal Investment Strategies.................................. 16
Principal Investment Risks....................................... 16
Performance History.............................................. 18
Your Expenses.................................................... 19

LIBERTY ACORN FOREIGN FORTY 20
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Investment Goal.................................................. 20
Principal Investment Strategies.................................. 20
Principal Investment Risks....................................... 20
Performance History.............................................. 23
Your Expenses.................................................... 24

YOUR ACCOUNT 25
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How to Buy Shares................................................ 25
Eligible Investors............................................... 26
Price of Fund Shares............................................. 28
How to Exchange Shares........................................... 28
How to Sell Shares............................................... 28
Other Information About Your Account............................. 30

MANAGING THE FUNDS 33
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Investment Advisor............................................... 33
Portfolio Managers............................................... 33

OTHER INVESTMENT
STRATEGIES AND RISKS 36
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The Information Edge............................................. 36
Stock Strength Comes First....................................... 36
Derivative Strategies............................................ 37
Temporary Defensive Strategies................................... 37

FINANCIAL HIGHLIGHTS 38
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</TABLE>

---------------------------------
Not FDIC May Lose Value
------------------
Insured No Bank Guarantee
---------------------------------
<PAGE>

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Liberty Acorn Fund
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INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn Fund seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------
Liberty Acorn Fund invests primarily in the stocks of small- and medium-sized
companies. The Fund generally invests in the stocks of companies with
capitalizations of less than $2 billion.

The Fund believes that these smaller companies, which are not as well known by
financial analysts, may offer higher return potential than the stocks of larger
companies.

Liberty Acorn Fund typically looks for companies with:

. A strong business franchise that offers growth potential.
. Products and services that give a company a competitive advantage.
. A stock price the Fund's advisor believes is reasonable relative to the
assets and earning power of the company.

Liberty Acorn Fund invests the majority of its assets in U.S. companies, but
also may invest up to 33% of its assets in companies outside the U.S. in
developed markets (for example, Japan, Canada and United Kingdom) and emerging
markets (for example, Mexico, Brazil and Korea).

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) that
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

Management risk means that the advisor's stock selections and other investment
decisions might produce losses or cause the Fund to underperform when compared
to other funds with a similar investment goal.

Market risk means that security prices in a market, sector or industry may move
down. Downward movements will reduce the value of your investment. Because of
management and market risk, there is no guarantee that the Fund will achieve its
investment goal or perform favorably compared with competing funds.

---
2
<PAGE>

Liberty Acorn Fund

Equity risk is the risk that stock prices will fall over short or extended
periods of time. Although the stock market has historically outperformed other
asset classes over the long term, the equity market tends to move in cycles and
individual stock prices may fluctuate drastically from day-to-day and may
underperform other asset classes over an extended period of time. Individual
companies may report poor results or be negatively affected by industry and/or
economic trends and developments. The prices of securities issued by such
companies may suffer a decline in response. These price movements may result
from factors affecting individual companies, industries or the securities market
as a whole.

Smaller companies and mid-capitalization companies are more likely than larger
companies to have limited product lines, operating histories, markets or
financial resources. They may depend heavily on a small management team. Stocks
of smaller companies and mid-capitalization companies may trade less frequently,
may trade in smaller volumes and may fluctuate more sharply in price than stocks
of larger companies. In addition, they may not be widely followed by the
investment community, which can lower the demand for their stock.

Foreign securities are subject to special risks. Foreign stock markets can be
extremely volatile. Fluctuations in currency exchange rates may impact the value
of foreign securities without a change in the intrinsic value of those
securities. The liquidity of foreign securities may be more limited than
domestic securities, which means that the Fund may, at times, be unable to sell
foreign securities at desirable prices. Brokerage commissions, custodial fees
and other fees are generally higher for foreign investments. In addition,
foreign governments may impose withholding taxes which would reduce the amount
of income and capital gains available to distribute to shareholders. Other risks
include the following: possible delays in the settlement of transactions or the
notification of income; less publicly available information about companies; the
impact of political, social or diplomatic events; and possible seizure,
expropriation or nationalization of the company or its assets or imposition of
currency exchange controls.

Emerging markets are subject to additional risk. The risks of foreign
investments are typically increased in less developed countries, which are
sometimes referred to as emerging markets. For example, political and economic
structures in these countries may be new and developing rapidly, which may cause
instability. Their securities markets may be underdeveloped. These countries are
also more likely than developed countries to experience high levels of
inflation, deflation or currency devaluations, which could hurt their economies
and securities markets, and to expropriate or nationalize a company or its
assets.

---
3
<PAGE>

Liberty Acorn Fund

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times, the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of its assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

---
4
<PAGE>

Liberty Acorn Fund

UNDERSTANDING PERFORMANCE

Calendar year total return shows the Fund's Class Z share performance for each
of the last ten complete calendar years. They include the effects of Fund
expenses.

Average annual total return is a measure of the Fund's performance over the past
one-year, five-year and ten-year periods. They include the effects of Fund
expenses.

The Fund's return is compared to the S&P 500 Index and the Russell 2000 Index.
The S&P 500 Index is a broad market-weighted average of large U.S. blue-chip
companies. The Russell 2000 Index is a market-weighted index of 2000 small
companies formed by taking the largest 3000 companies and eliminating the
largest 1000 of those companies. Unlike the Fund, indices are not investments,
do not incur fees or expenses and are not professionally managed. It is not
possible to invest directly in indices.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------
The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year, five years and ten years. The chart and table are
intended to illustrate some of the risks of investing in the Fund by showing the
changes in the Fund's performance. All returns include the reinvestment of
dividends and distributions. As with all mutual funds, past performance does not
predict the Fund's future performance.

--------------------------------------------------------------------------------
Calendar-Year Total Returns (Class Z)
--------------------------------------------------------------------------------

[CHART]

1990 (17.52%)
1991 47.35%
1992 24.23%
1993 32.32%
1994 (7.45%)
1995 20.80%
1996 22.55%
1997 24.98%
1998 6.02%
1999 33.38%

For period shown in bar chart: Best quarter: 4th quarter 1999, +21.94%

Worst quarter: 3rd quarter 1990, -23.77%

--------------------------------------------------------------------------------
Average Annual Total Returns -- for periods ended December 31, 1999
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Inception Date 1 Year 5 Years 10 Years
<S> <C> <C> <C> <C>
Class Z 6/10/70 33.38% 21.21% 17.07%
---------------------------------------------------------------------------------
S&P 500 n/a 21.04% 28.56% 18.21%
---------------------------------------------------------------------------------
Russell 2000 n/a 21.26% 16.69% 13.34%
</TABLE>

---
5
<PAGE>

Liberty Acorn Fund

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. Fund operating expenses remain the same

. Assumes reinvestment of all dividends and distributions

YOUR EXPENSES
--------------------------------------------------------------------------------
Expenses are one of several factors to consider before you invest in a mutual
fund. The tables below describe the fees and expenses you may pay when you buy,
hold and sell shares of the Fund.

--------------------------------------------------------------------------------
Shareholder Fees (paid directly from your investment)
--------------------------------------------------------------------------------

Maximum sales charge (load) on purchases None
--------------------------------------------------------------
Maximum deferred sales charge (load) on redemptions None
--------------------------------------------------------------
Redemption fee (%) (as a percentage of amount redeemed) None

--------------------------------------------------------------------------------
Annual Fund Operating Expenses (deducted directly from Fund assets)
--------------------------------------------------------------------------------

Management fees/(1)/ (%) .69
---------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
---------------------------------------------------------------
Other expenses (%) .16
---------------------------------------------------------------
Total annual fund operating expenses (%) .85
---------------------------------------------------------------
(1) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

--------------------------------------------------------------------------------
Example Expenses (your actual costs may be higher or lower)
--------------------------------------------------------------------------------
1 Year 3 Years 5 Years 10 Years

$87 $271 $471 $1,049

---
6
<PAGE>

--------------------------------------------------------------------------------
Liberty Acorn International
--------------------------------------------------------------------------------

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn International seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------
Liberty Acorn International invests primarily in stocks of non-U.S. small- and
medium-sized companies. The Fund generally invests in the stocks of companies
based outside the U.S. with capitalizations of less than $5 billion.

The Fund believes that smaller companies - particularly outside the U.S. - that
are not as well known by financial analysts may offer higher return potential
than the stocks of larger companies.

Liberty Acorn International typically looks for companies with:

Liberty Acorn International is an international fund and invests the majority
(under normal market conditions, at least 75%) of its total assets in the stocks
of foreign companies based in developed markets (for example, Japan, Canada and
the United Kingdom) and emerging markets (for example, Mexico, Brazil and
Korea).

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

---
7
<PAGE>

by industry and/or economic trends and developments. The prices of securities
issued by such companies may suffer a decline in response. These price movements
may result from factors affecting individual companies, industries or the
securities market as a whole.

---
8
<PAGE>

Liberty Acorn International

companies to the risk of rapid product obsolescence. The price of many
technology stocks has risen based on projections of future earnings and company
growth. If a company does not perform as expected, the price of the stock could
decline significantly. Many technology companies are currently operating at a
loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

---
9
<PAGE>

Liberty Acorn International

UNDERSTANDING PERFORMANCE

Calendar year total return shows the Fund's Class Z share performance for each
completed calendar year since it commenced operations. They include the effects
of Fund expenses.

Average annual total return is a measure of the Fund's performance over the past
one-year, five-year and life of the funds periods. They include the effects of
Fund expenses.

The Fund's return is compared to Morgan Stanley's Europe, Australasia and Far
East Index (EAFE), an index of companies throughout the world in proportion to
world stock market capitalizations, excluding the U.S. and Canada, and the EMI
(world ex-U.S.) Salomon Smith Barney's index of the bottom 20% of
institutionally investable capital of countries, selected by Salomon and
excluding the U.S. Unlike the Fund, indices are not investments, do not incur
fees or expenses and are not professionally managed. It is not possible to
invest directly in indices.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------
The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year, five years and the life of the Fund. The chart and
table are intended to illustrate some of the risks of investing in the Fund by
showing the changes in the Fund's performance. All returns include the
reinvestment of dividends and distributions. As with all mutual funds, past
performance does not predict the Fund's future performance.

--------------------------------------------------------------------------------
Calendar Year Total Returns/(1)/
--------------------------------------------------------------------------------

[CHART]

Year Return
---- ------

1993 49.11%
1994 (3.80%)
1995 8.93%
1996 20.65%
1997 0.19%
1998 15.43%
1999 79.19%

For period shown in bar chart: Best quarter: 4th quarter 1999, +41.63%

Worst quarter: 3rd quarter 1998, -16.05%

--------------------------------------------------------------------------------
Average Annual Total Returns -- for periods ended December 31, 1999/(1)/
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Inception Date 1 Year 5 Years Life of the Fund
<S> <C> <C> <C> <C>
Class Z 9/23/92 79.19% 22.19% 21.71%
---------------------------------------------------------------------------------------
EAFE N/A 26.96% 12.83% 13.50%
---------------------------------------------------------------------------------------
EMI (world ex-U.S.) N/A 23.52% 7.21% 9.48%
</TABLE>

(1) The Fund's performance in 1999 was achieved during a period of unusual
market conditions that are unlikely to continue.

---
10
<PAGE>

Liberty Acorn International

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. Fund operating expenses remain the same

. Assumes reinvestment of all dividends and distributions

Maximum sales charge (load) on purchases None
-----------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions None
-----------------------------------------------------------
Redemption fee (%) (as a percentage of
amount redeemed) None

Management fees/(2)/ (%) .81
-----------------------------------------------------------
Distribution and service (12b-1) fees (%) None
-----------------------------------------------------------
Other expenses (%) .30
-----------------------------------------------------------
Total annual fund operating expenses (%) 1.11
-----------------------------------------------------------
(2) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

1 Year 3 Years 5 Years 10 Years

$113 $353 $612 $1,352

___
11
<PAGE>

--------------------------------------------------------------------------------
Liberty Acorn USA
--------------------------------------------------------------------------------

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn USA seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------
Liberty Acorn USA invests primarily in stocks of small- and medium-sized U.S.
companies. The Fund generally invests in the stocks of U.S. companies with
capitalizations of less than $2 billion.

The Fund believes that these smaller companies, which are not as well known by
financial analysts, may offer higher return potential than the stocks of larger
companies.

Liberty Acorn USA typically looks for companies with:

. A strong business franchise that offers growth potential.

. Products and services that give a company a competitive advantage.

. A stock price the Fund's advisor believes is reasonable relative to the assets
and earning power of the company.

The Fund generally invests substantially all of its assets in U.S. companies
and, under normal market conditions, will invest at least 65% of its assets in
U.S. companies.

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

___
12
<PAGE>

Liberty Acorn USA

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

___
13
<PAGE>

Liberty Acorn USA

UNDERSTANDING PERFORMANCE

Calendar year total return shows the Fund's Class Z share performance for each
completed calendar year since it commenced operations. They include the effects
of Fund expenses.

Average annual total return is a measure of the Fund's performance over the past
one-year, three-year and life of the Fund periods. They include the effects of
Fund expenses.

The Fund's return is compared to the Russell 2000 Index. The Russell 2000 Index
is a market-weighted index, with dividends reinvested, of 2000 small companies
formed by taking the largest 3000 companies and eliminating the largest 1000 of
those companies. Unlike the Fund, an index is not an investment, does not incur
fees or expenses and is not professionally managed. It is not possible to invest
directly in an index.
================================================================================

PERFORMANCE HISTORY
--------------------------------------------------------------------------------
The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of a broad measure of market
performance for one year, three years and the life of the Fund. The chart and
table are intended to illustrate some of the risks of investing in the Fund by
showing the changes in the Fund's performance. All returns include the
reinvestment of dividends and distributions. As with all mutual funds, past
performance does not predict the Fund's future performance.

--------------------------------------------------------------------------------
Calendar Year Total Returns
--------------------------------------------------------------------------------

[CHART APPEARS HERE]

Year Return
---- ------

1997 32.30%
1998 5.79%
1999 23.02%

For period shown in bar chart: Best quarter: 4th quarter 1999, +18.93%
Worst quarter: 3rd quarter 1998, -19.25%

--------------------------------------------------------------------------------
Average Annual Total Returns - for periods ended December 31, 1999
--------------------------------------------------------------------------------

Inception Date 1 Year 3 Years Life of the Fund

Class Z 9/4/96 23.02% 19.86% 23.28%
--------------------------------------------------------------------------------
Russell 2000 N/A 21.26% 13.08% 14.65%

___
14
<PAGE>

Liberty Acorn USA

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. Fund operating expenses remain the same

. Assumes reinvestment of all dividends and distributions

Maximum sales charge (load) on purchases None
--------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions None
--------------------------------------------------------------
Redemption fee (%) (as a percentage of
amount redeemed, if applicable) None

--------------------------------------------------------------------------------
Annual Fund Operating Expenses (deduced directly from Fund assets)
--------------------------------------------------------------------------------

Management fees/(1)/ (%) .93
--------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
--------------------------------------------------------------
Other expenses (%) .22
--------------------------------------------------------------
Total annual fund operating expenses (%) 1.15
--------------------------------------------------------------
(1) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

1 Year 3 Years 5 Years 10 Years

$117 $365 $633 $1,398

___
15
<PAGE>

--------------------------------------------------------------------------------
Liberty Acorn Twenty
--------------------------------------------------------------------------------

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn Twenty seeks long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------
Liberty Acorn Twenty invests primarily in the stocks of medium- to larger-sized
U.S. companies. The Fund is a non-diversified fund that takes advantage of its
advisor's research and stock-picking capabilities to invest in a limited number
of companies (between 20-25) with market capitalizations of $2 billion to $12
billion.

The Fund believes that companies within this capitalization range are not as
well known by financial analysts, and may offer higher return potential than the
stocks of companies with capitalizations above $12 billion.

Liberty Acorn Twenty typically looks for companies with:

Although the Fund does not buy securities with a short-term view, there is no
restriction on the length of time the Fund must hold a security. To the extent
the Fund buys and sells securities frequently, its transaction costs will be
higher (which may adversely affect the Fund's performance) and it may realize
additional capital gains.

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

___
16
<PAGE>

Liberty Acorn Twenty

As a non-diversified mutual fund, the Fund is allowed to invest a greater
percentage of its total assets in the securities of a single issuer. This may
concentrate issuer risk and, therefore, the Fund may have an increased risk of
loss compared to a similar diversified mutual fund.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

___
17
<PAGE>

Liberty Acorn Twenty

UNDERSTANDING PERFORMANCE

Calendar year total return shows the Fund's Class Z share performance for each
completed calendar year since it commenced operations. They include the effects
of Fund expenses.

Average annual total return is a measure of the Fund's performance over the past
one-year and the life of the Fund periods. They include the effects of Fund
expenses.

The Fund's return is compared to the S&P MidCap 400 Index. The S&P MidCap 400 is
an unmanaged, market value-weighted index of 400 midcap U.S. companies. Unlike
the Fund, an index is not an investment, does not incur fees or expenses and is
not professionally managed. It is not possible to invest directly in an index.
================================================================================

PERFORMANCE HISTORY
--------------------------------------------------------------------------------
The bar chart below shows the Fund's performance for the past year by
illustrating the Fund's calendar year total return for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of a broad measure of market
performance for one year and the life of the Fund. The chart and table are
intended to illustrate some of the risks of investing in the Fund by showing the
changes in the Fund's performance. All returns include the reinvestment of
dividends and distributions. Performance results include the effect of expense
reduction arrangements. If these arrangements were not in place, then the
performance results would have been lower. Any expense reduction arrangements
may be discontinued at any time. As with all mutual funds, past performance does
not predict the Fund's future performance.

--------------------------------------------------------------------------------
Calendar Year Total Returns
--------------------------------------------------------------------------------

[CHART APPEARS HERE]

Year Return
---- ------
1999 29.30%

For period shown in bar chart: Best quarter: 4th quarter 1999, +14.35%
Worst quarter: 3rd quarter 1999, -7.13%

Inception Date 1 Year Life of Fund

Class Z 11/23/98 29.30% 34.20%
--------------------------------------------------------------------------------
S&P MidCap 400 N/A 14.72% 24.49%

___
18
<PAGE>

Liberty Acorn Twenty

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. The table does not take into account any
expense reduction arrangements discussed in the footnotes to the Annual Fund
Operating Expenses table. It uses the following hypothetical conditions:

. $10,000 initial investment

. 5% total return for each year

. Fund operating expenses remain the same

. Assumes reinvestment of all dividends and distributions

================================================================================

Maximum sales charge (load) on purchases None
--------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions None
--------------------------------------------------------------
Redemption fee (%) (as a percentage of
amount redeemed) None

Management fees/(1)/ (%) 0.90
--------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
--------------------------------------------------------------
Other expenses (%) 0.51
--------------------------------------------------------------
Total annual fund operating expenses/(2)/ (%) 1.41
--------------------------------------------------------------
(1) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

(2) The Fund's Advisor has voluntarily agreed to reimburse the Fund for any
ordinary operating expenses (exclusive of distribution and service fees,
interest, taxes and extraordinary expenses, if any) exceeding 1.35% of the
average annual net assets for Class Z. This arrangement may be modified or
terminated by either the Fund or its advisor on 30 days' notice. As a
result, the actual total annual Fund operating expenses for Class Z would
be 1.35%.

1 Year 3 Years 5 Years 10 Years

$144 $446 $771 $1,691

___
19
<PAGE>

--------------------------------------------------------------------------------
Liberty Acorn Foreign Forty
--------------------------------------------------------------------------------

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn Foreign Forty seeks long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------
Liberty Acorn Foreign Forty invests primarily in the stocks of medium- and
larger-sized companies based in developed markets (for example, Japan, Canada
and United Kingdom) outside the U.S. The Fund invests in at least three
countries. The Fund is a non-diversified Fund that takes advantage of its
advisor's research and stock-picking capabilities to invest in a limited number
of foreign companies (between 40-60) with market capitalizations of $5 billion
to $15 billion.

Liberty Acorn Foreign Forty typically looks for companies with:

Liberty Acorn Foreign Forty is an international fund and invests the majority of
its assets in the stocks of foreign companies based in developed markets outside
the U.S.

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

___
20
<PAGE>

Liberty Acorn Foreign Forty

___
21
<PAGE>

Liberty Acorn Foreign Forty

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

___
22
<PAGE>

Liberty Acorn Foreign Forty

UNDERSTANDING PERFORMANCE

Calendar year total return shows the Fund's Class Z share performance for each
completed calendar year since it commenced operations. They include the effects
of Fund expenses.

Average annual total return is a measure of the Fund's performance over the past
one-year and the life of the Fund periods. They include the effects of Fund
expenses.

The Fund's return is compared to the SSB Cap Range $2-10B Index. The SSB World
ex-U.S. Cap Range $2-10 Billion Index is Salomon Smith Barney's two to ten
billion U.S. dollar security market subset of its Broad Market Index. It
represents a midcap developed market index, excluding the U.S. Unlike the Fund,
an index is not an investment, does not incur fees or expenses and is not
professionally managed. It is not possible to invest directly in an index.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------
The bar chart below shows changes in the Fund's performance for the past year by
illustrating the Fund's calendar year total return for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of a broad measure of market
performance for one year and the life of the Fund. The chart and table are
intended to illustrate some of the risks of investing in the Fund by showing the
changes in the Fund's performance. All returns include the reinvestment of
dividends and distributions. Peformance results include the effect of expense
reduction arrangements, if any. If these arrangements were not in place, then
the performance results would have been lower. Any expense reduction
arrangements may be discontinued at any time. As with all mutual funds, past
performance does not predict the Fund's future performance.

--------------------------------------------------------------------------------
Calendar Year Total Returns/1/
--------------------------------------------------------------------------------

[CHART]

1999 81.60%

For period shown in bar chart: Best quarter: 4th quarter 1999, +46.65%
Worst quarter: 3rd quarter 1999, -3.90%

--------------------------------------------------------------------------------
Average Annual Total Returns - for periods ended December 31, 1999/1/
--------------------------------------------------------------------------------

Inception Date 1 Year Life of Fund

Class Z 11/23/98 81.60% 86.84%
--------------------------------------------------------------------------------
SSB Cap Range $2-10B N/A 23.52% 24.72%
--------------------------------------------------------------------------------
(1) The Fund's performance during 1999 was achieved in a period of unusual
market conditions that are unlikely to continue.

___
23
<PAGE>

Liberty Acorn Foreign Forty

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

. $10,000 initial investment

. 5% total return for each year

. Fund operating expenses remain the same

. Assumes reinvestment of all dividends and distributions

Maximum sales charge (load) on purchases None
--------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions None
--------------------------------------------------------------
Redemption fee (%) (as a percentage of
amount redeemed) None

Management fees/(2)/ (%) 0.95
--------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
--------------------------------------------------------------
Other expenses (%) 0.62
--------------------------------------------------------------
Total annual fund operating expenses/(3)/ (%) 1.57
--------------------------------------------------------------
(2) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

(3) The Fund's advisor has voluntarily agreed to reimburse the Fund for any
ordinary operating expenses (exclusive of distribution and service fees,
interest, taxes and extraordinary expenses, if any) exceeding 1.45% of the
average annual net assets for Class Z. This arrangement may be modified or
terminated by either the Fund or its advisor on 30 days' notice. As a
result, the actual total annual Fund operating expenses for Class Z would be
1.45%.

1 Year 3 Years 5 Years 10 Years

$160 $496 $855 $1,867

___
24
<PAGE>

--------------------------------------------------------------------------------
Your Account
--------------------------------------------------------------------------------

HOW TO BUY SHARES
--------------------------------------------------------------------------------
If you are an Eligible Investor your shares will be bought at the next
calculated price (described below), after the Fund receives your purchase
request in "good form." "Good form" means that your payment has been received
and your application is complete, including all necessary signatures. The Funds
reserve the right to refuse a purchase order for any reason, including if a Fund
believes that doing so would be in the best interest of the Funds and its
shareholders.

--------------------------------------------------------------------------------
Outlined below are the various options for buying shares:
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Method Instructions
<S> <C>
-----------------------------------------------------------------------------------------------------------
By check For new accounts, send a completed application and check made payable to the Fund
(new account) to the transfer agent, Liberty Funds Services, Inc., P.O. Box 1722, Boston, MA
02105-1722.
-----------------------------------------------------------------------------------------------------------
By check For existing accounts, fill out and return the additional investment stub
(existing account) included in your quarterly statement, or send a letter of instruction including
your Fund name and account number with a check made payable to the Fund to
Liberty Funds Services, Inc., P.O. Box 1722, Boston, MA 02105-1722.
-----------------------------------------------------------------------------------------------------------
By exchange You may acquire shares by exchanging shares you own in one Fund for shares of the
same class of another Liberty Acorn Fund at no additional cost. You also may
exchange your Class Z shares of a Fund for Class Z or, if there are no Class Z
shares, Class A shares of certain other funds distributed by Liberty Funds
Distributor, Inc., at net asset value without a sales charge. See the SAI for a
listing of the funds currently available. There may be an additional charge if
exchanging from a money market fund. To exchange by telephone, call
1-800-962-1585.
-----------------------------------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your bank account to your Fund
account. To wire funds to your Fund account, call 1-800-962-1585 to obtain a
control number and the wiring instructions.
-----------------------------------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically transferring money from your bank
transfer (existing account to your Fund account by calling 1-800-962-1585. Electronic funds
account) transfers may take up to two business days to settle and be considered in "good
form." You must set up this feature prior to your telephone request. Be sure to
complete the appropriate section of the application.
-----------------------------------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments automatically from your bank
investment plan account to your Fund account. You can select a pre-authorized amount to be sent
via electronic funds transfer. Be sure to complete the appropriate section of
the application for this feature.
-----------------------------------------------------------------------------------------------------------
By dividend You may automatically invest dividends distributed by one Liberty Acorn Fund into
diversification the same class of shares of another Liberty Acorn Fund at no additional sales
charge. To invest your dividends in another Fund, call 1-800-962-1585.
-----------------------------------------------------------------------------------------------------------
Through an Contact your financial professional.
intermediary
</TABLE>

___
25
<PAGE>

Your Account

ELIGIBLE INVESTORS
--------------------------------------------------------------------------------
Only Eligible Investors may purchase Class Z shares of the Funds, directly or by
exchange. Eligible Investors are subject to different minimum investment
requirements. Eligible Investors and their applicable investment minimums are:

$1,000 minimum initial investment

. any shareholder (or family member of such shareholder) who owned shares of
any of the Liberty Acorn funds on September 29, 2000 (when all of the
Trust's then outstanding shares were re-designated Class Z shares) and who
has since then continued to own shares of any funds distributed by Liberty
Funds Distributor, Inc.;

. any trustee of Liberty Acorn Trust, any employee of Liberty WAM, or a
member of the family of the trustee or employee; and

. any person or entity listed in the account registration for any account
(such as joint owners, trustees, custodians, and designated beneficiaries)
that held shares of any of the funds of Liberty Acorn Trust on September
29, 2000 and that has since then continued to hold shares of any funds
distributed by Liberty Funds Distributor, Inc.

$100,000 minimum initial investment

. any client of a broker-dealer or registered investment advisor that
recommends Fund shares and charges an asset-based fee;

. any insurance company, trust company or bank, which is purchasing shares
for its own account;

. any endowment, investment company or foundation; and

. any client of an investment advisory affiliate of the distributor if the
client meets certain criteria established by the distributor and its
affiliate.

No minimum initial investment

. any person investing all or part of the proceeds of a distribution, "roll
over" or transfer of assets into a Liberty IRA from, any deferred
compensation plan which was a shareholder of any of the Liberty Acorn funds
on September 29, 2000, in which the investor was a participant and through
which the investor invested in one or more of the Liberty Acorn funds
immediately prior to the distribution, transfer or roll over; and

. any retirement plan with aggregate assets of at least $5 million at the
time it purchases Class Z shares and which is purchasing shares directly
from the distributor or through a third party broker-dealer.

___
26
<PAGE>

Your Account

If you have any questions about your eligibility to purchase Class Z shares of
the Fund, please call 800-962-1585. If you hold Fund shares through a broker-
dealer or other financial institution, your eligibility to purchase Class Z
shares may differ depending on that institution's policies.

The Fund reserves the right to change the criteria for eligible investors and
these investment minimums. No minimum investment applies to accounts
participating in the automatic investment plan.

The Fund also reserves the right to refuse a purchase order for any reason,
including if it believes that doing so would be in the best interest of the Fund
and its shareholders.

___
27
<PAGE>

Your Account

CHOOSING A SHARE CLASS

The Fund offers one class of shares in this prospectus -- Class Z.

The Fund also offers three additional classes of shares -- Class A, B, and C
shares are available through a separate prospectus. Each share class has its own
sales charge and expense structure. Determining which share class is best for
you depends on the dollar amount you are investing and the number of years for
which you are willing to invest. Based on your personal situation, your
investment advisor can help you decide which class of shares makes the most
sense for you. In general, anyone who is eligible to purchase Class Z shares,
which do not incur Rule 12b-1 fees or sales charges, should do so in preference
over other classes.

================================================================================

PRICE OF FUND SHARES
--------------------------------------------------------------------------------
Your purchases of Class Z shares generally are at net asset value, which is the
value of a Fund share without any sales charge. Class Z shares are not subject
to an initial sales charge when purchased, or a contingent deferred sales charge
when sold.

If you purchase Class Z shares of the Funds through certain broker-dealers,
banks or other intermediaries (intermediaries), they may charge a fee for their
services. They may also place limits on your ability to use services the Funds
offer. There are no sales charges or limitations if you purchase shares
directly from the Funds, except as described in this prospectus.

If an intermediary is an agent or designee of the Funds, orders are processed at
the net asset value next calculated after the intermediary receives the order.
The intermediary must segregate any orders it receives after the close of
regular trading on the NYSE and transmit those orders separately for execution
at the net asset value next determined.

HOW TO EXCHANGE SHARES
--------------------------------------------------------------------------------
You may exchange your Class Z shares of the Funds for shares of another Fund at
no additional charge. You also may exchange your Class Z shares of any Fund for
Class Z shares or, if there are no Class Z shares, Class A shares of certain
other funds distributed by Liberty Funds Distributor, Inc., at net asset value
without a sales charge. Unless your account is part of a tax-deferred
retirement plan, an exchange is a taxable event. Therefore, you may realize a
gain or a loss for tax purposes. The Funds may terminate your exchange
privilege if the advisor determines that your exchange activity is likely to
adversely impact its ability to manage the Funds. To exchange by telephone, call
1-800-962-1585.

HOW TO SELL SHARES
--------------------------------------------------------------------------------
You may sell shares of a Fund on any regular business day that the New York
Stock Exchange (NYSE) is open.

When a Fund receives your sales request in "good form," shares will be sold at
the next calculated net asset value. In "good form" means that money used to
purchase your shares is fully collected. When selling shares by letter of
instruction, "good form" also means (i) your letter has complete instructions,
the proper signatures and signature guarantees, and (ii) any other required
documents are attached. A signature guarantee is designed to protect you and
Liberty Acorn from fraud. Signature guarantees can be obtained from a commercial
bank, broker-dealer, credit union (if authorized under state law), securities
exchange or association. A notary public cannot provide a signature guarantee.
For additional documents required for sales by corporations, agents, fiduciaries
and surviving joint owners, please call 1-800-962-1585. Retirement plan accounts
have special requirements; please call 1-800-962-1585 for more information.

___
28
<PAGE>

Your Account

A Fund will generally send proceeds from the sale to you within seven days
(usually on the next business day after your request is received in "good
form"). However, if you purchased your shares by check, a Fund may delay
sending the proceeds from the sale of your shares for up to 15 days after your
purchase to protect against checks that are returned. No interest will be paid
on uncashed redemption checks. Redemption proceeds may be paid in securities
rather than cash, under certain circumstances. For more information, see the
paragraph "Non-Cash Redemptions" under the section "How to Sell Shares" in the
Statement of Additional Information.

--------------------------------------------------------------------------------
Outlined below are the various options for selling shares:
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Method Instructions
-----------------------------------------------------------------------------------------------------------
<S> <C>
By exchange You may sell shares by exchanging from a Fund into Class Z shares or Class A
shares of another fund distributed by Liberty Funds Distributor, Inc. at no
additional cost. To exchange by telephone, call 1-800-962-1585.
-----------------------------------------------------------------------------------------------------------
By telephone You may sell shares by telephone and request that a check be sent to your address
of record by calling 1-800-422-3737, unless you have notified the Fund of an
address change within the previous 30 days. The dollar limit for telephone sales
is $100,000 in a 30-day period. You do not need to set up this feature in
advance of your call. Certain restrictions apply to retirement accounts. For
details, call 1-800-962-1585.
-----------------------------------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock power form to the address
below. In your letter of instruction, note the Fund's name, share class, account
number, and the dollar value or number of shares you wish to sell. All account
owners must sign the letter, and signatures must be guaranteed by either a bank,
a member firm of a national stock exchange or another eligible guarantor
institution. Additional documentation is required for sales by corporations,
agents, fiduciaries, surviving joint owners and individual retirement account
owners. For details, call 1-800-962-1585.

Mail your letter of instruction to Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
-----------------------------------------------------------------------------------------------------------
By wire You may sell shares and request that the proceeds be wired to your bank. You
must set up this feature prior to your telephone request. Be sure to complete
the appropriate section of the account application for this feature.
-----------------------------------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be electronically transferred
funds transfer to your bank. Proceeds may take up to two business days to be received by your
bank. You must set up this feature prior to your request. Be sure to complete
the appropriate section of the account application for this feature.
-----------------------------------------------------------------------------------------------------------
Systematic Withdrawal You may automatically sell a specified dollar amount or percentage on a monthly,
Plan quarterly or semiannual basis if your account balance is at least $5,000 and have
the proceeds sent to you. This feature is not available if you hold your shares
in certificate form. Be sure to complete the appropriate section of the account
application for this feature.
-----------------------------------------------------------------------------------------------------------
Through an Contact your financial professional. Financial professionals may charge fees for
Intermediary their services.
</TABLE>

___
29
<PAGE>

Your Account

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------
How the Funds' Share Price is Determined The price of a Fund's Class Z Shares is
its net asset value. The net asset value is determined at the close of regular
trading on the NYSE, usually 4:00 p.m. Eastern time, on each business day that
the NYSE is open (typically Monday through Friday).

When you request a transaction, it will be processed at the net asset value next
determined after your request is received in "good form" by Liberty Acorn (or an
authorized broker-dealer, financial services company, or other agent, some of
whom may charge a fee for their services). In most cases, in order to receive
that day's price, Liberty Acorn must receive your order before that day's
transactions are processed. If you request a transaction through an agent, that
agent must receive your order by the close of trading on the NYSE to receive
that day's price.

A Fund determines its net asset value for its Class Z shares by dividing total
net assets attributable to Class Z shares by the number of outstanding Class Z
shares. In determining the net asset value, the Fund must determine the price
of each security in its portfolio at the close of each trading day. Because
Liberty Acorn Fund, Liberty Acorn International and Liberty Acorn Foreign Forty
may hold securities that are traded on foreign exchanges, the value of these
Funds' securities may change on days when shareholders will not be able to buy
or sell Fund shares. This will affect the net asset value on the day it is next
determined. Securities for which market quotations are available are valued
each day at the current market value. However, where market quotations are
unavailable, or when the advisor believes that subsequent events have made them
unreliable, the Fund may use other data to determine the fair value of the
securities.

You can find the daily prices of some share classes for the Funds in most major
daily newspapers under the caption "Liberty." You can find daily prices for all
share classes by visiting the Funds' web site at www.acornfunds.com.

Share Certificates Share certificates are not available for Class Z shares.

___
30
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Each Fund earns income from the securities it holds. Each Fund also may realize
capital gains and losses on sales of its securities. A Fund distributes
substantially all of its net investment income and capital gains to
shareholders. As a shareholder, you are entitled to a portion of your Fund's
income and capital gains based on the number of shares you own at the time these
distributions are declared.

================================================================================

Dividends, Distributions, and Taxes Each Fund has the potential to make the
following distributions:

--------------------------------------------------------------------------------
Types of Distributions
--------------------------------------------------------------------------------

Dividend Represents interest and dividends earned from securities
held by a Fund net of expenses incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of
securities held for more than 12 months and net short-term
capital gains, which are gains on sales of securities held
for a 12-month period or less.

Distribution Options Each Fund distributes dividends in June and December and
any capital gains (including short-term capital gains) at least annually. You
can choose one of the options listed in the table below for these distributions
when you open your account. To change your distribution option call 1-800-962-
1585.

If you do not indicate on your application your preference for handling
distributions, a Fund will automatically reinvest all distributions in
additional shares of the Fund.

--------------------------------------------------------------------------------
Distribution Options
--------------------------------------------------------------------------------

Reinvest all distributions in additional shares of your current fund
--------------------------------------------------------------------------------
Reinvest all distributions in shares of another Fund
--------------------------------------------------------------------------------
Receive dividends in cash (see options below) and reinvest capital gains
--------------------------------------------------------------------------------
Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is
returned as undeliverable, or if you do not cash a distribution check within six
months of the check date, the distribution will be reinvested in additional
shares of the Fund.

Tax Consequences Regardless of whether you receive your distributions in cash or
reinvest them in additional Fund shares, all Fund distributions are subject to
federal income tax. Depending on the state where you live, distributions may
also be subject to state and local income taxes.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in a Fund may have additional personal tax implications. Please
consult your tax advisor on foreign, federal, state, local or other applicable
tax laws.

___
31
<PAGE>

Your Account

In addition to the dividends and capital gains distributions made by each Fund,
you may realize a capital gain or loss when selling and exchanging shares of the
Fund. Such transactions may be subject to federal, state and local income tax.

Foreign Income Taxes A Fund may receive investment income from sources within
foreign countries, and that income may be subject to foreign income taxes at the
source. If your Fund pays non-refundable taxes to foreign governments during the
year, the taxes will reduce that Fund's dividends but will still be included in
your taxable income. You may be able to claim an offsetting credit or deduction
on your tax return for your share of foreign taxes paid by Liberty Acorn
International or Liberty Acorn Foreign Forty.

___
32
<PAGE>

--------------------------------------------------------------------------------
Managing the Fund
--------------------------------------------------------------------------------

INVESTMENT ADVISOR
--------------------------------------------------------------------------------

Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset Management,
L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago, Illinois
60606, is the Funds' investment advisor. Liberty WAM and its predecessor have
managed mutual funds, including the Funds, since 1992. In its duties as
investment advisor, Liberty WAM runs the Funds' day-to-day business, including
placing all orders for the purchase and sale of the Funds' portfolio securities.
As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

WAM was renamed Liberty WAM on September 29, 2000 when it became a wholly owned
subsidiary of Liberty Financial Companies, Inc. (Liberty), which in turn is a
majority owned indirect subsidiary of Liberty Mutual Insurance Company. For more
information about Liberty's acquisition of WAM, see the Statement of Additional
Information.

Liberty WAM earns the following advisory fees for managing the Funds.

--------------------------------------------------------------------------------
Fund Name Fund Fee as a % of
Average Net Assets
During 1999
--------------------------------------------------------------------------------
Liberty Acorn Fund .69%
Liberty Acorn International .81%
Liberty Acorn USA .93%
Liberty Acorn Twenty .90%
Liberty Acorn Foreign Forty .95%

Liberty WAM also receives an administrative services fee from each Fund at the
annual rate of .05% of that Fund's average daily net assets.

PORTFOLIO MANAGERS
--------------------------------------------------------------------------------
Liberty WAM uses a team to manage the Funds. Team members share responsibility
for providing ideas, information, and knowledge in managing the Funds, and each
team member has one or more particular areas of expertise. The portfolio
managers are responsible for making daily portfolio selection decisions, and
utilize the management team's input and advice when making buy and sell
determinations.

Ralph Wanger

Liberty Acorn Fund, Lead portfolio manager

Ralph Wanger is chief strategist of the Liberty Acorn Funds and has been
portfolio manager of Liberty Acorn Fund since its inception in 1970. He has been
president and a member of Liberty Acorn Trust's Board of Trustees since 1970.
Mr. Wanger has been president of Liberty WAM since September 29, 2000 and was a
principal of WAM before that date. He is a Chartered Financial Analyst (CFA),
and earned his BS and MS degrees in Industrial Management from the Massachusetts
Institute of Technology.

___
33
<PAGE>

Managing the Fund
Charles P. McQuaid
Liberty Acorn Fund, Co-portfolio manager

Charles McQuaid is a senior vice president and member of Liberty Acorn Trust's
Board of Trustees. He has been director of Domestic Research at Liberty WAM and
WAM, and was a principal of WAM until September 29, 2000. Mr. McQuaid has been a
member of Liberty Acorn Fund's management team since 1978. He is a CFA, and
earned his BBA from the University of Massachusetts and his MBA from the
University of Chicago.

Leah J. Zell
Liberty Acorn International, Lead portfolio manager

Leah Zell is a vice president of Liberty Acorn Trust, and was a principal of WAM
before its acquisition by Liberty. She has managed Liberty Acorn International
since its inception in 1992, and was named lead portfolio manager in 1997. She
has worked with Liberty Acorn Fund's international securities since 1984. Ms.
Zell also manages the foreign portfolio of an investment company whose shares
are offered only to non-U.S. investors. She is a CFA and earned her BA and PhD
from Harvard University.

Margaret M. Forster
Liberty Acorn International, Co-portfolio manager

Margaret Forster is a vice president of Liberty Acorn Trust and became co-
portfolio manager of Liberty Acorn International in May 1999. She has been a
member of the international analytical team at Liberty WAM and WAM since 1994,
and was a principal of WAM from January 1999 to September 29, 2000. Prior to
that, Ms. Forster was a professor of finance at Northwestern and Ohio State
Universities, and an economist with the International Monetary Fund. She is a
CFA. Her degrees include a BS from Universidade de Sao Paulo, Escola
Politecnica, Brazil, and an MBA, MS and PhD from Cornell University.

Robert A. Mohn
Liberty Acorn USA, Lead portfolio manager

Robert Mohn is a vice president of Liberty Acorn Trust. He has been a member of
the domestic analytical team at Liberty WAM and WAM since 1992, and was a
principal of WAM from 1995 to September 29, 2000. He has managed Liberty Acorn
USA since its inception in 1996, and also manages a mutual fund underlying
variable insurance products and the U.S. portfolio of an investment company
whose shares are offered only to non-U.S. investors. He is a CFA and holds a BS
from Stanford University and an MBA from the University of Chicago.

___
34
<PAGE>

Managing the Fund

John H. Park
Liberty Acorn Twenty, Lead portfolio manager

John Park is a vice president of Liberty Acorn Trust, and has managed Liberty
Acorn Twenty since its inception in 1998. He has been a member of the domestic
investment team at Liberty WAM and WAM since 1993, and was a principal of WAM
from 1998 to September 29, 2000. Mr. Park is also manager of a mutual fund
underlying variable insurance products. He is a CFA and earned both his BA and
MBA degrees from the University of Chicago.

Marcel P. Houtzager
Liberty Acorn Foreign Forty, Co-portfolio manager

Marcel Houtzager is a vice president of Liberty Acorn Trust, and has managed
Liberty Acorn Foreign Forty since its inception in 1998. He has been a member of
the international analytical team at Liberty WAM and WAM since 1992, and was a
principal of WAM from 1995 to September 29, 2000. Mr. Houtzager also manages an
international mutual fund underlying variable insurance products and the foreign
portfolio of an investment company whose shares are offered only to non-U.S.
investors. He is a CFA and a CPA, and earned his BA from Pomona College and his
MBA from the University of California at Berkeley.

Roger D. Edgley
Liberty Acorn Foreign Forty, Co-portfolio manager

Roger Edgley is a vice president of Liberty Acorn Trust and became co-portfolio
manager of Liberty Acorn Foreign Forty in December 1999. He has been director of
International Research at Liberty WAM and WAM, and was a principal of WAM from
January 1999 to September 29, 2000. Mr. Edgley has been a member of the
international analytical team at Liberty WAM and WAM since 1994. Prior to that,
Mr. Edgley was a securities analyst in Hong Kong. He is a CFA and was educated
in the United Kingdom, completing his MSc degree from the London School of
Economics.

___
35
<PAGE>

--------------------------------------------------------------------------------
Other Investment Strategies and Risks
--------------------------------------------------------------------------------

UNDERSTANDING THE FUNDS' OTHER INVESTMENT STRATEGIES AND RISKS

The principal investment strategies and risks for each Fund are described under
"The Funds - Principal Investment Strategies" and "The Funds - Principal
Investment Risks." In seeking to meet its investment goal, a Fund may also
invest in other securities and use certain investment techniques. These
securities and investment techniques offer opportunities and carry various
risks.

Liberty WAM may elect not to buy any of these securities or use any of these
techniques unless it believes that doing so will help a Fund achieve its
investment goal. A Fund may not always achieve its investment goal.

Additional information about each Fund's securities and investment techniques,
as well as the its fundamental and non-fundamental investment policies, is
contained in the Statement of Additional Information.

--------------------------------------------------------------------------------

The first portion of this prospectus describes the Funds' principal investment
strategies and their associated risks. This section provides more detail about
the Funds' investment strategies, and describes other investments a Fund may
make and the risks associated with them. In seeking to achieve its investment
goal, a Fund may invest in various types of securities and engage in various
investment techniques, which are not the principal focus of the Fund and
therefore are not described in this prospectus. These types of securities and
investment practices are identified and discussed in the Funds' Statement of
Additional Information, which you may obtain free of charge (see back cover).
Approval by the Funds' shareholders is not required to modify or change the
Funds' investment goals or investment strategies.

THE INFORMATION EDGE
--------------------------------------------------------------------------------
The Funds invest in entrepreneurially managed smaller, mid-sized and larger
companies that they believe are not as well known by financial analysts and
whose domination of a niche creates the opportunity for superior earnings-growth
potential.

In making investments for the Funds, Liberty WAM relies primarily on
independent, internally generated research to uncover companies that may be less
well known than the more popular names. To find these companies, Liberty WAM
looks for growth potential, financial strength and fundamental value. Liberty
WAM may identify what it believes are important economic, social or
technological trends (for example, the growth of out-sourcing as a business
strategy, or the productivity gains from the increasing use of technology) and
try to identify companies it thinks will benefit from these trends.

Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------

. superior technology . low debt . reasonable stock
. innovative marketing . adequate working price relative to
. managerial skill capital growth potential
. market niche . conservative . valuable assets
. good earnings accounting practices
prospects . adequate profit
. strong demand for margin
product

A strong balance sheet Once Liberty WAM
gives management uncovers an attractive
The realization of this greater flexibility to company, it identifies
growth potential would pursue strategic a price that it
likely produce superior objectives and is believes would also
performance that is essential to maintaining make the stock a good
sustainable over time. a competitive advantage. value.
--------------------------------------------------------------------------------

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------
Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty
WAM's analysts talk to top management, vendors, suppliers and competitors,
whenever possible.

In managing the Funds, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least 2-5 years). However,
securities purchased on a long-term basis may be sold within 12 months after
purchase due to changes in the circumstances of a particular company or
industry, or changes in general market or economic conditions.

___
36
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------
A Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money than the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------

At times, Liberty WAM may determine that adverse market conditions make it
desirable to temporarily suspend a Fund's normal investment activities. During
such times, a Fund may, but is not required to, invest in cash or high-quality,
short-term debt securities, without limit. Taking a temporary defensive position
may prevent the Fund from achieving its investment goal.

___
37
<PAGE>

--------------------------------------------------------------------------------
Financial Highlights
--------------------------------------------------------------------------------
The financial highlights tables are intended to help you understand the Funds'
financial performance. Information is shown for each Fund's last five fiscal
years or since the Fund's inception, and for the six months ended June 30, 2000.
The Funds' fiscal year runs from January 1 to December 31. Certain information
reflects financial results for a single Fund share. The total returns in each
table represent the rate that you would have earned (or lost) on an investment
in a Fund (assuming reinvestment of all dividends and distributions). The
information with respect to the six month period ended June 30, 2000 is
unaudited. The information with respect to the last five fiscal years is
audited. For periods up to and including the year ended 1999, this information
has been derived from the Funds' financial statements which have been audited by
Ernst & Young LLP, independent auditors, whose report, along with the Funds'
audited financial statements, is included in the Funds' annual report. You can
request a free annual report by calling 1-800-9-ACORN-9 (800-922-6769).

--------------------------------------------------------------------------------
Liberty Acorn Fund
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Six months
ended June 30, Year ended December 31,
For a share outstanding throughout each period 2000 1999 1998 1997 1996 1995

(unaudited)

Class Z Class Z Class Z Class Z Class Z Class Z
<S> <C> <C> <C> <C> <C> <C>
Net asset value, beginning of period $18.53 $16.85 $16.99 $15.04 $13.60 $12.24
------------------------------------------------------------------------------------------------------------------------------------

Income from Investment Operations:

Net investment income .06 .09 .04 .15 .09 .11
------------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on
investments, foreign currency and futures (.32) 5.22 .91 3.57 2.93 2.42
------------------------------------------------------------------------------------------------------------------------------------
Total from investment operations (.26) 5.31 .95 3.72 3.02 2.53
------------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income (0.05) (.09) (.03) (.16) (.11) (.09)
------------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (1.00) (3.54) (1.06) (1.61) (1.47) (1.08)
------------------------------------------------------------------------------------------------------------------------------------
Total distributions (1.05) (3.63) (1.09) (1.77) (1.58) (1.17)
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $17.22 $18.53 $16.85 $16.99 $15.04 $13.60
------------------------------------------------------------------------------------------------------------------------------------
Total return (a) (1.41)% 33.4% 6.0% 25.0% 22.6% 20.8%
------------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net assets .84%* .85% .84% .56% .57% .57%
------------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income to
average net assets .62%* .49% .30% .75% .53% .89%
------------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 35%* 34% 24% 32% 33% 29%
------------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period (in millions) $3,818 $3,921 $3,549 $3,681 $2,842 $2,399
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(a) Total return is not annualized for periods less than one year.
* Annualized

___
38
<PAGE>

Financial Highlights

--------------------------------------------------------------------------------
Liberty Acorn International
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Six months ended
June 30, Year ended December 31,
For a share outstanding throughout each period 2000 1999 1998 1997 1996 1995
(unaudited)
Class Z Class Z Class Z Class Z Class Z Class Z
<S> <C> <C> <C> <C> <C> <C>
Net asset value, beginning of period $35.33 $20.82 $18.39 $19.61 $16.59 $15.24
------------------------------------------------------------------------------------------------------------------------------------

Income from Investment Operations:

Net investment income --- .83 .17 .40 .13 .16
------------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain (loss) on
investments, foreign currency and futures (1.34) 15.45 2.68 (.34) 3.29 1.20
------------------------------------------------------------------------------------------------------------------------------------
Total from investment operations (1.34) 16.28 2.85 .06 3.42 1.36
------------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income (.66) (.22) (.15) (.38) (.12) ---
------------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.51) (1.55) (.27) (.90) (.28) (.01)
------------------------------------------------------------------------------------------------------------------------------------
Total distributions (1.17) (1.77) (.42) (1.28) (.40) (.01)
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $32.82 $35.33 $20.82 $18.39 $19.61 $16.59
------------------------------------------------------------------------------------------------------------------------------------
Total return (a) (3.8)% 79.2% 15.4% 0.2% 20.7% 8.9%
------------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net assets 1.06%* 1.11% 1.12% 1.19% 1.17% 1.22%
------------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income to
average net assets .01%* .12% .86% .58% .51% .90%
------------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 76%* 46% 37% 39% 34% 26%
------------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period (in millions) $2,984 $2,868 $1,725 $1,623 $1,773 $1,276
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(a) Total return is not annualized for periods less than one year.

* Annualized

___
39
<PAGE>

Financial Highlights

--------------------------------------------------------------------------------
Liberty Acorn USA
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Inception
September 4
Six months Through December
ended June 30, Year ended December 31, 31,
For a share outstanding throughout each period 2000 1999 1998 1997 1996

(unaudited)
Class Z Class Z Class Z Class Z Class Z
<S> <C> <C> <C> <C> <C>
Net asset value, beginning of period $16.75 $14.80 $15.12 $11.65 $10.00
------------------------------------------------------------------------------------------------------------------------------------

Income from Investment Operations:

Net investment loss (a) (.02) --- (.07) (.07) (.02)
------------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on
investments (2.67) 3.32 .87 3.83 1.67
------------------------------------------------------------------------------------------------------------------------------------
Total from investment operations (2.69) 3.32 .80 3.76 1.65
------------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income --- --- --- --- ---
------------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.32) (1.37) (1.12) (.29) ---
------------------------------------------------------------------------------------------------------------------------------------
Total distributions (.32) (1.37) (1.12) (.29) ---
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $13.74 $16.75 $14.80 $15.12 $11.65
------------------------------------------------------------------------------------------------------------------------------------
Total return (c) (16.1)% 23.0% 5.8% 32.3% 16.5%
------------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net assets (b) 1.13%* 1.15% 1.20% 1.35% 1.85%*
------------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment loss to average net
assets (.27)%* 0.00% (.42)% (.49)% (.99)%*
------------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 65%* 49% 42% 33% 20%*
------------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period (in millions) $ 305 $ 371 $ 281 $ 185 $ 53
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

a) Net investment loss per share was based upon the average shares outstanding
during the period.

b) In accordance with a requirement by the Securities and Exchange Commission,
the ratio of expenses to average net assets for Liberty Acorn USA reflects
gross custodian fees. This ratio net of custodian fees paid indirectly
would have been 1.79% for the period ended December 31, 1996.

c) Total return is not annualized for periods less than one year.

* Annualized

___
40
<PAGE>

Financial Highlights
--------------------------------------------------------------------------------
Liberty Acorn Twenty
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Six months ended Inception November 23
June 30, Year Ended December 31, Through December 31,
For a share outstanding throughout each period 2000 1999 1998

(unaudited)
Class Z Class Z Class Z
<S> <C> <C> <C>
Net asset value, beginning of period $13.70 $ 10.71 $10.00
------------------------------------------------------------------------------------------------------------------------------------

Income from Investment Operations:

Ratios/supplemental data:
Ratio of expenses to average net assets
(b)(c) 1.37%* 1.37% 1.41%*
------------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income (loss)
to average net assets (c) (.57)%* (.62)% .22%*
------------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 170%* 101% 1.73%*
------------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period (in millions) $ 61 $ 68 $ 34
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(a) Net investment income (loss) per share was based upon the average shares
outstanding during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the Liberty Acorn Twenty ratio reflects total expenses prior to the
reduction of custodian fees for cash balances it maintains with the
custodian ("custodian fees paid indirectly"). This ratio net of custodian
fees paid indirectly would have been 1.35% for the period ended December
31, 1998, the year ended December 31, 1999 and the six months ended June
30, 2000.

(c) Liberty Acorn Twenty was reimbursed by the Advisor for certain net expenses
from November 23, 1998 through December 31, 1999. Without the
reimbursement, the ratio of expenses (prior to custodian fees paid
indirectly) to average net assets and the ratio of net investment income to
average net assets would have been 1.83% and (.21%), respectively, for the
period ended 12/31/98, 1.41% and (.66%), respectively, for the year ended
12/31/99 and 1.40% and (.60%), respectively, for the six months ended June
30, 2000.

(d) Total return is not annualized for periods less than one year.

*Annualized

___
41
<PAGE>

Financial Highlights
--------------------------------------------------------------------------------
Liberty Acorn Foreign Forty
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Six months ended Inception November 23
June 30, Year Ended Through December 31
For a share outstanding throughout each period 2000 1999 1998

(unaudited)
Class Z Class Z Class Z
<S> <C> <C> <C>
Net asset value, beginning of period $19.93 $ 11.00 $10.00
------------------------------------------------------------------------------------------------------------------------------------

Income from Investment Operations:

Net investment loss (a) --- (.02) (.01)
------------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain (loss) on
investments (.12) 8.98 1.01
------------------------------------------------------------------------------------------------------------------------------------
Total from investment operations (.12) 8.96 1.00
------------------------------------------------------------------------------------------------------------------------------------
Less Distributions:
Dividends from net investment income (.03) --- ---
------------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and unrealized
gains reportable for federal income taxes (.11) (.03) ---
------------------------------------------------------------------------------------------------------------------------------------
Total Distributions (.14) (.03) ---
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $19.67 $ 19.93 $11.00
------------------------------------------------------------------------------------------------------------------------------------
Total return (d) (0.6%) 81.6% 10.0%
------------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net assets (b)(c) 1.37%* 1.48% 1.73%*
------------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment loss to average net
assets (c) (.03%)* (.17%) (.78%)*
------------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 74%* 60% 90%*
------------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period (in millions) $ 144 $ 107 $ 16
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(a) Net investment loss per share was based upon the average shares outstanding
during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the Liberty Acorn Foreign Forty ratio reflects total expenses prior to the
reduction of custodian fees for cash balances it maintains with the
custodian ("custodian fees paid indirectly"). This ratio net of custodian
fees paid indirectly would have been 1.45% for the period ended December
31, 1998, and the year ended December 31, 1999.

(c) Liberty Acorn Foreign Forty was reimbursed by the Advisor for certain net
expenses from November 23, 1998 through December 31, 1999. Without the
reimbursement, the ratio of expenses (prior to custodian fees paid
indirectly) to average net assets and the ratio of net investment income to
average net assets would have been 2.70% and (1.75%), respectively, for the
period ended 12/31/98 and 1.57% and (.26%), respectively, for the year
ended 12/31/99.

(d) Total return is not annualized for periods less than one year.

* Annualized

___
42
<PAGE>

--------------------------------------------------------------------------------
Notes
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

___
43
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------
You can get more information about the Fund's investments in the Funds' semi-
annual and annual reports to shareholders. The annual report contains a
discussion of the market conditions and investment strategies that significantly
affected the Funds' performance over its last fiscal year.

You may wish to read the Statement of Additional Information for more
information on the Funds and the securities in which they invest. The Statement
of Additional Information is incorporated into this prospectus by reference,
which means that it is considered to be part of this prospectus.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about Liberty Acorn by
writing or calling Liberty Acorn's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-9-ACORN-9
www.acornfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

You can review and copy information about the Funds by visiting the following
location, and you can obtain copies, upon payment of a duplicating fee by
electronic request at the E-mail address [email protected] or by writing the:

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust: 811-01829
(formerly Acorn Investment Trust)

--------------------------------------------------------------------------------
[LOGO] L I B E R T Y
-----------------
F U N D S

ALL-STAR.COLONIAL.CRABBE HUSON.NEWPORT.STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (C)2000
One Financial Center, Boston, MA 02111-2621, 1-800-426-3750
www.libertyfunds.com

<PAGE>

LIBERTY ACORN FUND
LIBERTY ACORN INTERNATIONAL
LIBERTY ACORN USA
LIBERTY ACORN TWENTY
LIBERTY ACORN FOREIGN FORTY

Supplement dated September 29, 2000
to Prospectus dated September 29, 2000 of Liberty Acorn Trust

Enhanced pricing schedule on the Liberty Acorn Funds through February 28, 2001.

We're celebrating the newest additions to our growing fund family with an
enhanced commission schedule on A, B and C shares of the Liberty Acorn Funds and
a reduced sales load on A share purchases.

Effective October 16, 2000 - February 28, 2001:
<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------
Purchase Price Reduced Upfront Sales Load** Enhanced Dealer Commission
------------------------------------------------------------------------------------------------------------
<S> <C> <C>
Less than $250,000 A share - 2.00% A share - 4.00%
B share - 5.00%
C share - 2.00%
------------------------------------------------------------------------------------------------------------
$250,000 to less than $500,000 A share - 2.00% A share - 3.50%
B share - 4.50%
C share - 2.00%
------------------------------------------------------------------------------------------------------------
$500,000 to $1,000,000 A share - 2.00% A share - 2.50%
B share - 3.75%
C share - 2.00%
------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<CAPTION>
Liberty Acorn Fund Liberty Acorn International
<S> <C>
A share - 53015P106 A share - 53015P841
B share - 53015P205 B share - 53015P833
C share - 53015P304 C share - 53015P825

Liberty Acorn USA Liberty Acorn Foreign Forty
A share - 53015P502 A share - 53015P791
B share - 53015P601 B share - 53015P783
C share - 53015P700 C share - 53015P775

Liberty Acorn Twenty
A share - 53015P882
B share - 53015P874
C share - 53015P866
</TABLE>

**Reduced sales load on A share purchases only.

Liberty Funds Distributor, Inc. One Financial Center, Boston, MA 02111-2621
VAL-19/892C-0900 (00/1660)

<PAGE>

LIBERTY ACORN FUND
LIBERTY ACORN INTERNATIONAL
LIBERTY ACORN USA
LIBERTY ACORN TWENTY
LIBERTY ACORN FOREIGN FORTY

Supplement dated September 29, 2000
to Prospectus dated September 29, 2000 of Liberty Acorn Trust

IRA Accounts. Liberty Acorn will not accept new IRA accounts (including
Roth IRAs, SIMPLE-IRAs and SEP-IRAs) until October 30, 2000.
<PAGE>

LIBERTY ACORN FUND Prospectus, September 29, 2000

Class A, B and C Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

-----------------------------------------------------------------------------
T A B L E O F C O N T E N T S

<TABLE>
<S> <C>
LIBERTY ACORN FUND 2
-----------------------------------------------------------------------------
Investment Goal.......................................................... 2
Principal Investment Strategies.......................................... 2
Principal Investment Risks............................................... 2
Performance History...................................................... 4
Your Expenses............................................................ 5

YOUR ACCOUNT 6
-----------------------------------------------------------------------------
How to Buy Shares........................................................ 6
Sales Charges............................................................ 7
How to Exchange Shares................................................... 11
How to Sell Shares....................................................... 11
Fund Policy on Trading of Fund Shares.................................... 12
Distribution and Service Fees............................................ 13
Other Information About Your Account..................................... 13

MANAGING THE FUND 17
-----------------------------------------------------------------------------
Investment Advisor....................................................... 17
Portfolio Managers....................................................... 17

OTHER INVESTMENT STRATEGIES AND RISKS 19
-----------------------------------------------------------------------------
The Information Edge..................................................... 19
Stock Strength Comes First............................................... 19
Derivative Strategies.................................................... 20
Temporary Defensive Strategies........................................... 20

FINANCIAL HIGHLIGHTS 21
-----------------------------------------------------------------------------
</TABLE>

----------------------------
Not FDIC | May Lose Value
------------------
Insured | No Bank Guarantee
----------------------------

<PAGE>

Liberty Acorn Fund

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn Fund seeks to provide long-term growth of capital.

The Fund believes that these smaller companies, which are not as well known by
financial analysts, may offer higher return potential than the stocks of larger
companies.

Liberty Acorn Fund typically looks for companies with:

Additional strategies that are not principal investment strategies and the risks
associated with them are described later in this prospectus under "Other
Investment Strategies and Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

_____
2
<PAGE>

Liberty Acorn Fund

from factors affecting individual companies, industries or the securities market
as a whole.

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of its assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

_____
3
<PAGE>

Liberty Acorn Fund

UNDERSTANDING PERFORMANCE

CALENDAR YEAR TOTAL RETURNS show the Fund's Class Z share performance for each
of the last ten complete calendar years. They include the effects of Class Z
expenses. Class A, Class B and Class C shares are subject to sales charges,
12b-1 fees and different expenses that are not reflected in the bar chart. If
these amounts were reflected, returns would be less than those shown.

AVERAGE ANNUAL TOTAL RETURNS are measures of the Fund's Class Z performance over
the past one-year, five-year and ten-year periods. They include the effects of
Class Z expenses. The table shows for each class the Class Z performance
restated to reflect the effect of sales charges of each class.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------
Because Class A, Class B and Class C shares have not been offered for a full
calendar year, the information provided in the bar chart below shows changes in
the Fund's performance from year to year by illustrating the Fund's calendar
year total returns for its Class Z shares. Class Z shares are offered to certain
investors through separate prospectuses. The performance table following the bar
chart shows how the Fund's average annual returns for (1) the Class Z shares and
(2) the Class Z shares, restated to reflect the sales charges of the Class A,
Class B and Class C shares, respectively, compared with those of broad measures
of market performance for one year, five years and ten years. The chart and
table are intended to illustrate some of the risks of investing in the Fund by
showing the changes in the Fund's Class Z performance. All returns include the
reinvestment of dividends and distributions. As with all mutual funds, past
performance does not predict the Fund's future performance.

Calendar Year Total Returns (Class Z)/(1)/

________________________________________________________________________________

[BAR CHART]

Year Return
---- ------
1990 (17.52%)
1991 47.35%
1992 24.23%
1993 32.32%
1994 (7.45%)
1995 20.80%
1996 22.55%
1997 24.98%
1998 6.02%
1999 33.38%

________________________________________________________________________________

For period shown in bar chart:
Best quarter: 4th quarter 1999, +21.94%
Worst quarter: 3rd quarter 1990, -23.77%

(1) Class Z shares are not offered through this prospectus, but Class A, Class B
and Class C shares would have substantially similar annual returns because
the shares are invested in the same portfolio of securities and these
returns differ only to the extent that the classes do not have the same
expenses.

Average Annual Total Returns-- for periods ended December 31, 1999/(2)/

Inception Date 1 Year 5 Years 10 Years

Class A 9/29/00 25.71% 19.78% 16.38%
----------------------------------------------------------------------------
Class B 9/29/00 28.38% 21.02% 17.07%
----------------------------------------------------------------------------
Class C 9/29/00 32.38% 21.21% 17.07%
----------------------------------------------------------------------------
Class Z 6/10/70 33.38% 21.21% 17.07%
----------------------------------------------------------------------------
S&P 500 N/A 21.04% 28.56% 18.21%
----------------------------------------------------------------------------
Russell 2000 N/A 21.26% 16.69% 13.34%
----------------------------------------------------------------------------

(2) Class A, Class B, and Class C are new classes of shares. Their performance
information includes returns of the Fund's Class Z shares (the oldest
existing fund class) for periods prior to the inception of the newer classes
of shares. Class Z returns are not restated to reflect any differences in
expenses (such as Rule 12b-1 fees) between Class Z shares and the newer
classes of shares. If differences in expenses were reflected, the returns
for prior to the inception of the newer classes of shares would be lower.
Class Z shares were initially offered on June 10, 1970; Class A, Class B
and Class C shares were initially offered on September 29, 2000.

____
4
<PAGE>

Liberty Acorn Fund

UNDERSTANDING EXPENSES

Sales Charges are paid directly by shareholders to Liberty Funds Distributor,
Inc., the Fund's distributor.

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, 12b-1 fees and administrative costs
including pricing and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

. assumes Class B shares convert to Class A shares after eight years

YOUR EXPENSES
--------------------------------------------------------------------------------

Expenses are one of several factors to consider before you invest in a mutual
fund. The tables below describe the fees and expenses you may pay when you buy,
hold and sell shares of the Fund.

Shareholder Fees /(3)/ (paid directly from your investment)

<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Maximum sales charge (load) on purchases (%)
(as a percentage of the offering price) 5.75 None None
------------------------------------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions (%) (as a percentage of the
lesser of purchase price or redemption price) 1.00/(4)/ 5.00 1.00
------------------------------------------------------------------------------------------
Redemption fee (5) (5) (5)

</TABLE>

(3) A $10 annual fee is deducted from accounts of less than $1,000 and paid to
the transfer agent.

(4) This charge applies only to certain Class A shares bought without an initial
sales charge that are sold within 18 months of purchase.

(5) There is a $7.50 charge for wiring sale proceeds to your bank.

Annual Fund Operating Expenses (deducted directly from fund assets)

<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Management Fees/(6)/(%) .69 .69 .69
--------------------------------------------------------------------------------------
Distribution and service (12b-1) fees (%) .35 1.00 1.00
--------------------------------------------------------------------------------------
Other expenses (%) .33 .33 .33
--------------------------------------------------------------------------------------
Total annual fund operating expenses (%) 1.37 2.02 2.02
</TABLE>

(6) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

Example Expenses (your actual costs may be higher or lower)

<TABLE>
<CAPTION>
Class 1 Year 3 Years 5 Years 10 Years
<S> <C> <C> <C> <C>
Class A: $ 706 $ 984 $1,282 $2,127
-----------------------------------------------------------------------------------------------
Class B: did not sell your shares $ 205 $ 634 $1,088 $2,181

sold all your shares at
the end of the period $ 705 $ 934 $1,288 $2,181
-----------------------------------------------------------------------------------------------
Class C: did not sell your shares $ 205 $ 634 $1,088 $2,348

sold all your shares at
the end of the period $ 305 $ 634 $1,088 $2,348
</TABLE>
____
5
<PAGE>

Your Account

INVESTMENT MINIMUMS

Initial Investment.................................................... $1,000
Subsequent Investments................................................ $50
Automatic Investment Plan*............................................ $50
Retirement Plans*..................................................... $25

* The initial investment minimum of $1,000 is waived on this plan.

The Fund reserves the right to change these investment minimums. The Fund also
reserves the right to refuse a purchase order for any reason, including if it
believes that doing so would be in the best interest of the Fund and its
shareholders.

HOW TO BUY SHARES
--------------------------------------------------------------------------------

Your financial advisor can help you establish an appropriate investment
portfolio, buy shares and monitor your investments. When the Fund receives your
purchase request in "good form," your shares will be bought at the next
calculated public offering price. "Good form" means that you placed your order
with your brokerage firm or your payment has been received and your application
is complete, including all necessary signatures.

Outlined below are the various options for buying shares:

Method Instructions

Through your Your financial advisor can help you establish your
financial advisor account and buy Fund shares on your behalf. Your
financial advisor may charge you fees for executing the
purchase for you.
--------------------------------------------------------------------------------
By check For new accounts, send a completed application and check
(new account) made payable to the Fund to the transfer agent, Liberty
Funds Services, Inc., P.O. Box 1722, Boston, MA 02105-
1722.
--------------------------------------------------------------------------------

By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your quarterly
statement, or send a letter of instruction including
your Fund name and account number with a check made
payable to the Fund to Liberty Funds Services, Inc.,
P.O. Box 1722, Boston, MA 02105-1722.
--------------------------------------------------------------------------------

____
6
<PAGE>

Your Account

CHOOSING A SHARE CLASS

The Fund offers three classes of shares in this prospectus -- Class A , B and C.
Each share class has its own sales charge and expense structure. Determining
which share class is best for you depends on the dollar amount you are investing
and the number of years for which you are willing to invest. If your financial
advisor firm does not participate in the Class B discount program, purchases of
$250,000 or more must be for Class A or Class C shares only. Purchases of $1
million or more can be made only in Class A shares. Based on your personal
situation, your financial advisor can help you decide which class of shares
makes the most sense for you.

The Fund also offers an additional class of shares, Class Z shares, to certain
institutional and other investors. Class Z shares are made available through
separate prospectuses provided to eligible institutional and other
investors.

SALES CHARGES
--------------------------------------------------------------------------------
You may be subject to an initial sales charge when you purchase, or a contingent
deferred sales charge (CDSC) when you sell, shares of the Fund. These sales
charges are described below. In certain circumstances, these sales charges are
waived, as described below and in the Statement of Additional Information.

Class A shares Your purchases of Class A shares generally are at the public
offering price. This price includes a sales charge that is based on the amount
of your initial investment when you open your account. A portion of the sales
charge is the commission paid to the financial advisor firm on the sale of Class
A shares. The sales charge you pay on additional investments is based on the
total amount of your purchase and the current value of your account. The amount
of the sales charge differs depending on the amount you invest as shown in the
table below.

Class A Sales Charges

<TABLE>
<CAPTION>
% of offering
As a % of price
the public As a % retained by
offering of your financial
Amount of purchase price investment advisor firm
<S> <C> <C> <C>
Less than $50,000 5.75 6.10 5.00
----------------------------------------------------------------------------------------------
$50,000 to less than $100,000 4.50 4.71 3.75
----------------------------------------------------------------------------------------------
$100,000 to less than $250,000 3.50 3.63 2.75
----------------------------------------------------------------------------------------------
$250,000 to less than $500,000 2.50 2.56 2.00
----------------------------------------------------------------------------------------------
$500,000 to less than $1,000,000 2.00 2.04 1.75
----------------------------------------------------------------------------------------------
$1,000,000 or more 0.00 0.00 0.00
----------------------------------------------------------------------------------------------
</TABLE>

Class A shares bought without an initial sales charge in accounts aggregating $1
million to $25 million at the time of purchase are subject to a 1.00% CDSC if
the shares are sold within 18 months of the time of purchase. Subsequent Class
A share purchases that bring your account value above $1 million are subject to
a CDSC if redeemed within 18 months of the date of purchase. The 18-month
period begins on the first day of the month following each purchase. The CDSC
does not apply to retirement plans purchasing shares through a fee-based
program.

For Class A share purchases of $1 million or more, financial advisors receive a
commission from the distributor as follows:

Purchases Over $1 Million

Amount purchased Commission %

First $3 million 1.00
-----------------------------------------------------------------------
$3 million to less than $5 million 0.80
-----------------------------------------------------------------------
$5 million to less than $25 million 0.50
-----------------------------------------------------------------------
$25 million or more 0.25

The commission to financial advisors for Class A share purchases of $25 million
or more is paid over 12 months but only to the extent the shares remain
outstanding.

For Class A share purchases by participants in certain group retirement plans
offered through a fee-based program, financial advisors received a 1.00%
commission from the distributor on all purchases of less than $3 million.

____
7
<PAGE>

Your Account

UNDERSTANDING CONTINGENT DEFERRED SALES CHARGES (CDSC)

Certain investments in Class A, B and C shares are subject to a CDSC, a sales
charge applied at the time you sell your shares. You will pay the CDSC only on
shares you sell within a certain amount of time after purchase. The CDSC
generally declines each year until there is no charge for selling shares. The
CDSC is applied to the net asset value at the time of purchase or sale,
whichever is lower. For purposes of calculating the CDSC, the start of the
holding period is the month-end of the month in which the purchase is made.
Shares you purchase with reinvested dividends or capital gains are not subject
to a CDSC. When you place an order to sell shares, your Fund will automatically
sell first those shares not subject to a CDSC and then those you have held the
longest. This policy helps reduce and possibly eliminate the potential impact of
the CDSC.

Reduced Sales Charges for Larger Investments There are two ways for you to pay a
lower sales charge when purchasing Class A shares. The first is through Rights
of Accumulation. If the combined value of the Fund accounts maintained by you,
your spouse or your minor children reaches a discount level (according to the
chart on the previous page), your next purchase will receive the lower sales
charge. The second is by signing a Statement of Intent within 90 days of your
purchase. By doing so, you would be able to pay the lower sales charge on all
purchases by agreeing to invest a total of at least $50,000 within 13 months. If
your Statement of Intent purchases are not completed within 13 months, you will
be charged the applicable sales charge on the amount you had invested to that
date. In addition, certain investors may purchase shares at a reduced sales
charge or net asset value, which is the value of a Fund share excluding any
sales charges. See the Statement of Additional Information for a description of
these situations.

Class B shares Your purchases of Class B shares are at Class B shares' net asset
value. Class B shares have no front-end sales charge, but they do carry a CDSC
that is imposed only on shares sold prior to the completion of the periods shown
in the charts below. The CDSC generally declines each year and eventually
disappears over time. The distributor pays the financial advisor firm an
up-front commission on sales of Class B shares as depicted in the charts below.

Purchases of less than $250,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 5.00
-----------------------------------------------------------------------------
Through second year 4.00
-----------------------------------------------------------------------------
Through third year 3.00
-----------------------------------------------------------------------------
Through fourth year 3.00
-----------------------------------------------------------------------------
Through fifth year 2.00
-----------------------------------------------------------------------------
Through sixth year 1.00
-----------------------------------------------------------------------------
Longer than six years None

Commission to financial advisors is 5.00%.

Automatic conversion to Class A shares is eight years after purchase.

____
8
<PAGE>

Your Account

You can pay a lower CDSC and reduce the holding period when making purchases of
Class B shares through a financial advisor firm which participates in the Class
B share discount program for larger purchases as described in the charts below.
Some financial advisor firms are not able to participate because their record
keeping or transaction processing systems are not designed to accommodate these
reductions. For non-participating firms, purchases of Class B shares must be
less than $250,000. Consult your financial advisor to see whether it
participates in the discount program for larger purchases. For participating
firms, Rights of Accumulation apply, so that if the combined value of Fund
accounts maintained by you, your spouse or your minor children is at or above a
discount level, your next purchase will receive the lower CDSC and the
applicable reduced holding period.

Purchases of $250,000 to less than $500,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 3.00
-----------------------------------------------------------------------------
Through second year 2.00
-----------------------------------------------------------------------------
Through third year 1.00
-----------------------------------------------------------------------------
Longer than three years 0.00

Commission to financial advisors is 2.50%.

Automatic conversion to Class A shares is four years after purchase.

Purchases of $500,000 to less than $1 million:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold
-----------------------------------------------------------------------------
Through first year 3.00
-----------------------------------------------------------------------------
Through second year 2.00
-----------------------------------------------------------------------------
Through third year 1.00

Commission to financial advisors is 1.75%.

Automatic conversion to Class A shares is three years after purchase.

____
9
<PAGE>

Your Account

If you exchange into a Fund participating in the Class B share discount program
or transfer your Fund account from a financial advisor which does not
participate in the program to one who does, the exchanged or transferred shares
will retain the pre-existing CDSC but any additional purchases of Class B shares
which cause the exchanged or transferred account to exceed the applicable
discount level will receive the lower CDSC and the reduced holding period for
amounts in excess of the discount level. Your financial advisor will receive the
lower commission for purchases in excess of the applicable discount level. If
you exchange from a participating fund or transfer your account from a financial
advisor that does participate in the program into a fund or financial advisor
which does not, the exchanged or transferred shares will retain the pre-existing
CDSC but all additional purchases of Class B shares will be in accordance with
the higher CDSC and longer holding period of the non-participating fund or
financial advisor.

Class C shares Similar to Class B shares, your purchases of Class C shares are
at Class C's net asset value. Although Class C shares have no front-end sales
charge, they carry a CDSC of 1.00% that is applied to shares sold within the
first year after they are purchased. After holding shares for one year, you may
sell them at any time without paying a CDSC. The distributor pays the financial
advisor firm an up-front commission of 1.00% on sales of Class C shares.

Class C Sales Charges

Years after purchase % deducted when shares are sold

Through one year 1.00
--------------------------------------------------------------------------
Longer than one year 0.00

____
10
<PAGE>

Your Account

HOW TO EXCHANGE SHARES
--------------------------------------------------------------------------------
You may exchange your shares for shares of the same share class of another fund
distributed by Liberty Funds Distributor, Inc. at net asset value. If your
shares are subject to a CDSC, you will not be charged a CDSC upon the exchange.
However, when you sell the shares acquired through the exchange, the shares sold
may be subject to a CDSC, depending upon when you originally purchased the
shares you exchanged. For purposes of computing the CDSC, the length of time you
have owned your shares will be computed from the date of your original purchase
and the applicable CDSC will be the CDSC of the original fund. Unless your
account is part of a tax-deferred retirement plan, an exchange is a taxable
event. Therefore, you may realize a gain or a loss for tax purposes. The Fund
may terminate your exchange privilege if the advisor determines that your
exchange activity is likely to adversely impact its ability to manage the Fund.
To exchange by telephone, call 1-800-422-3737.

HOW TO SELL SHARES
--------------------------------------------------------------------------------
Your financial advisor can help you determine if and when you should sell your
shares. You may sell shares of the Fund on any regular business day that the New
York Stock Exchange (NYSE) is open.

When the Fund receives your sales request in "good form," shares will be sold at
the next calculated price. In "good form" means that money used to purchase your
shares is fully collected. When selling shares by letter of instruction, "good
form" also means (i) your letter has complete instructions, the proper
signatures and signature guarantees, (ii) you have included any certificates for
shares to be sold, and (iii) any other required documents are attached. A
signature guarantee is designed to protect you and Liberty Acorn from fraud.
Signature guarantees can be obtained from a commercial bank, broker-dealer,
credit union (if authorized under state law), securities exchange or
association. A notary public cannot provide a signature guarantee. For
additional documents required for sales by corporations, agents, fiduciaries and
surviving joint owners, please call 1-800-345-6611. Retirement plan accounts
have special requirements; please call 1-800-799-7526 for more information.

The Fund will generally send proceeds from the sale to you within seven days
(usually on the next business day after your request is received in "good
form"). However, if you purchased your shares by check, the Fund may delay
sending the proceeds from the sale of your shares for up to 15 days after your
purchase to protect against checks that are returned. No interest will be paid
on uncashed redemption checks. Redemption proceeds may be paid in securities
rather than cash, under certain circumstances. For more information, see the
paragraph "Non-Cash Redemptions" under the section "How to Sell Shares" in the
Statement of Additional Information.
____
11
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions

Through your You may call your financial advisor to place your sell
financial advisor order. To receive the current trading day's price, your
financial advisor firm must receive your request prior to
the close of the NYSE, usually 4:00 p.m. Eastern time.
--------------------------------------------------------------------------------
By exchange You or your financial advisor may sell shares by
exchanging from the Fund into the same share class of
another Liberty fund at no additional cost. To exchange
by telephone, call 1-800-422-3737.
--------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by
telephone and request that a check be sent to your
address of record by calling 1-800-422-3737, unless you
have notified the Fund of an address change within the
previous 30 days. The dollar limit for telephone sales is
$100,000 in a 30-day period. You do not need to set up
this feature in advance of your call. Certain
restrictions apply to retirement accounts. For details,
call 1-800-345-6611.
--------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock
power form along with any certificates to be sold to the
address below. In your letter of instruction, note your
Fund's name, share class, account number, and the dollar
value or number of shares you wish to sell. All account
owners must sign the letter, and signatures must be
guaranteed by either a bank, a member firm of a national
stock exchange or another eligible guarantor institution.
Additional documentation is required for sales by
corporations, agents, fiduciaries, surviving joint owners
and individual retirement account owners. For details,
call 1-800-345-6611.

By systematic You may automatically sell a specified dollar amount or
withdrawal plan percentage on a monthly, quarterly or semi-annual basis
if your account balance is at least $5,000 and have the
proceeds sent to you. This feature is not available if
you hold your shares in certificate form. Be sure to
complete the appropriate section of the account
application for this feature.
--------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may
take up to two business days to be received by your bank.
You must set up this feature prior to your request. Be
sure to complete the appropriate section of the account
application for this feature.

FUND POLICY ON TRADING OF FUND SHARES
--------------------------------------------------------------------------------

The Fund does not permit short-term or excessive trading. Excessive purchases,
redemptions or exchanges of Fund shares disrupt portfolio management and drive
Fund expenses higher. In order to promote the best interests of the Fund, the
Fund reserves the right to reject any purchase order or exchange request,
particularly from market timers or investors who, in the advisor's opinion, have
a pattern of short-term or excessive trading or whose trading has been or may be
disruptive to the Fund. The fund into which you would like to exchange also may
reject your request.

____
12
<PAGE>

Your Account

DISTRIBUTION AND SERVICE FEES
--------------------------------------------------------------------------------

The Fund has adopted a plan under Rule 12b-1 that permits it to pay the Fund's
distribution, marketing and other fees to support the sale and distribution of
Class A, B and C shares and certain services provided to you by your financial
advisor. The annual service fee may equal up to 0.25% for Class A, Class B and
Class C shares. The annual distribution fee may equal up to 0.10% for Class A
shares and 0.75% for Class B and Class C shares. Distribution and service fees
are paid out of the assets of these classes. Over time, these fees may reduce
the return on your investment and may cost you more than paying other types of
sales charges. Class B shares automatically convert to Class A shares after a
certain number of years, eliminating a portion of the distribution fee upon
conversion. Conversion may occur three, four or eight years after purchase,
depending on the program you purchased your shares under. See "Your Account;
Sales Charge" for the conversion schedule applicable to Class B shares.

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------

HOW THE FUND'S SHARE PRICE IS DETERMINED The price of each class of the Fund's
shares is based on its net asset value. The net asset value is determined at the
close of regular trading on the NYSE, usually 4:00 p.m. Eastern time, on each
business day that the NYSE is open (typically Monday through Friday).

When you request a transaction, it will be processed at the net asset value
(plus any applicable sales charges) next determined after your request is
received in "good form" by the distributor. In most cases, in order to receive
that day's price, the distributor must receive your order before that day's
transactions are processed. If you request a transaction through your financial
advisor's firm, the firm must receive your order by the close of trading on the
NYSE to receive that day's price.

The Fund determines its net asset value for each share class by dividing each
class's total net assets by the number of that class's outstanding shares. In
determining the net asset value, the Fund must determine the price of each
security in its portfolio at the close of each trading day. Because the Fund
holds securities that are traded on foreign exchanges, the value of these
securities may change on days when shareholders will not be able to buy or sell
Fund shares. This will affect the Fund's net asset value on the day it is next
determined. Securities for which market quotations are available are valued each
day at the current market value. However, where market quotations are not
available, or when the advisor believes that subsequent events have made them
unreliable, the Fund may use other data to determine the fair value of the
securities.

You can find the daily prices of some share classes for the Fund in most major
daily newspapers under the caption "Liberty." You can find daily prices for all
share classes by visiting the Fund's web site at www.libertyfunds.com.

ACCOUNT FEES If your account value falls below $1,000 (other than as a result of
depreciation in share value) you may be subject to an annual account fee of $10.
This fee is deducted from the account in June each year. Approximately 60 days
prior to the fee date, the Fund's transfer agent will send you written
notification of the upcoming fee. If

____
13
<PAGE>

Your Account

you add money to your account and bring the value above $1,000 prior to the fee
date, the fee will not be deducted.

Share Certificates Share certificates are not available for Class B and C
shares. Certificates will be issued for Class A shares only if requested. If you
decide to hold share certificates, you will not be able to sell your shares
until you have endorsed your certificates and returned them to the distributor.

____
14
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

The Fund earns income from the securities it holds. The Fund also may realize
capital gains and losses on sales of its securities. The Fund distributes
substantially all of its net investment income and capital gains to
shareholders. As a shareholder, you are entitled to a portion of the Fund's
income and capital gains based on the number of shares you own at the time these
distributions are declared.

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities
held by the Fund, net of expenses incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of
securities held for more than 12 months and net short-term
capital gains, which are gains on sales of securities held
for a 12-month period or less.

Distribution Options The Fund distributes dividends in June and December and
any capital gains (including short-term capital gains) at least annually. You
can choose one of the options listed in the table below for these distributions
when you open your account. To change your distribution option call 1-800-345-
6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
--------------------------------------------------------------------------------
Reinvest all distributions in shares of another fund
--------------------------------------------------------------------------------
Receive dividends in cash (see options below) and reinvest capital gains
--------------------------------------------------------------------------------
Receive all distributions in cash (with one of the following options)

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.
___
15
<PAGE>

Your Account

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

In addition to the dividends and capital gains distributions made by the Fund,
you may realize a capital gain or loss when selling and exchanging shares of the
Fund. Such transactions may be subject to federal, state and local income tax.

Foreign Income Taxes The Fund may receive investment income from sources within
foreign countries, and that income may be subject to foreign income taxes at the
source. If the Fund pays non-refundable taxes to foreign governments during the
year, the taxes will reduce the Fund's dividends but will still be included in
your taxable income.

____
16
<PAGE>

Managing the Fund

INVESTMENT ADVISOR
--------------------------------------------------------------------------------
Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset Management,
L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago, Illinois
60606, is the Fund's investment advisor. Liberty WAM and its predecessor have
managed mutual funds, including the Fund, since 1992. In its duties as
investment advisor, Liberty WAM runs the Fund's day-to-day business, including
placing all orders for the purchase and sale of the Fund's portfolio securities.
As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.69% of the Fund's
average daily net assets. Liberty WAM also receives an administrative services
fee from the Fund at the annual rate of .05% of the Fund's average daily net
assets.

PORTFOLIO MANAGERS
--------------------------------------------------------------------------------
Liberty WAM uses a team to manage the Fund. Team members share responsibility
for providing ideas, information, and knowledge in managing the Fund, and each
team member has one or more particular areas of expertise. The portfolio
managers are responsible for making daily investment decisions, and utilize the
management team's input and advice when making buy and sell determinations.

Ralph Wanger
Lead portfolio manager

Charles P. McQuaid
Co-portfolio manager

----
17
<PAGE>

Managing the Fund

member of Liberty Acorn Fund's management team since 1978. He is a CFA, and
earned his BBA from the University of Massachusetts and his MBA from the
University of Chicago.

___
18
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

The Fund's principal investment strategies and risks are described under
"Liberty Acorn Fund - Principal Investment Strategies" and Liberty Acorn Fund -
Principal Investment Risks." In seeking to meet its investment goal, the Fund
may also invest in other securities and use certain other investment techniques.
These securities and investment techniques offer opportunities and carry various
risks.

Liberty WAM may elect not to buy any of these securities or use any of these
techniques unless it believes that doing so will help the Fund achieve its
investment goal. The Fund may not always achieve its investment goal.

Additional information about the Fund's securities and investment techniques, as
well as the Fund's fundamental and non-fundamental investment policies, is
contained in the Statement of Additional Information.

The first portion of this prospectus describes the Fund's principal investment
strategies and their associated risks. This section provides more detail about
the Fund's investment strategies, and describes other investments the Fund may
make and the risks associated with them. In seeking to achieve its investment
goal, the Fund may invest in various types of securities and engage in various
investment techniques, which are not the principal focus of the Fund and
therefore are not described in this prospectus. These types of securities and
investment practices are identified and discussed in the Fund's Statement of
Additional Information, which you may obtain free of charge (see back cover).
Approval by the Fund's shareholders is not required to modify or change the
Fund's investment goal or investment strategies.

THE INFORMATION EDGE
--------------------------------------------------------------------------------

Liberty WAM invests in entrepreneurially managed smaller and mid-sized companies
that it believes are not as well known by financial analysts and whose
domination of a niche creates the opportunity for superior earnings-growth
potential. Liberty WAM may identify what it believes are important economic,
social or technological trends (for example, the growth of out-sourcing as a
business strategy, or the productivity gains from the increasing use of
technology) and try to identify companies it thinks will benefit from those
trends.

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock
. innovative marketing . adequate working price relative to
. managerial skill capital growth potential
. market niche . conservative . valuable assets
. good earnings accounting practices
prospects . adequate profit
. strong demand margin
for product

----
19
<PAGE>

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------
Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty WAM
analysts talk to top management, vendors, suppliers and competitors, whenever
possible.

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

Other Investment Strategies and Risks

securities purchased on a long-term basis may be sold within 12 months after
purchase due to changes in the circumstances of a particular company or
industry, or changes in general market or economic conditions.

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------
The Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money that the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------
At times, Liberty WAM may determine that adverse market conditions make it
desirable to temporarily suspend the Fund's normal investment activities.
During such times, the Fund may, but is not required to, invest in cash or high-
quality, short-term debt securities, without limit. Taking a temporary defensive
position may prevent the Fund from achieving its investment goal.

____
20
<PAGE>

Financial Highlights

The financial highlights tables are intended to help you understand the Fund's
financial performance. Because Class A, Class B and Class C shares are new
classes of shares, information is shown for the Fund's Class Z shares for the
last five fiscal years and for the six months ended June 30, 2000. The Fund's
fiscal year runs from January 1 to December 31. Class Z shares are offered to
certain investors through separate prospectuses. Certain information reflects
financial results for a single Fund share. The total returns in the table
represent the rate that you would have earned (or lost) on an investment in the
Fund (assuming reinvestment of all dividends and distributions). The information
with respect to the six month period ended June 30, 2000 is unaudited. The
information with respect to the last five years is audited. For periods up to
and including the year ended 1999, this information has been derived from the
Fund's financial statements which have been audited by Ernst & Young LLP,
independent auditors, whose report, along with the Fund's audited financial
statements, is included in the Fund's annual report. You can request a free
annual report by calling 1-800-426-3750.

Liberty Acorn Fund

<TABLE>
<CAPTION>
Six months
Ended Year Year Year Year Year
For a share outstanding throughout 6/30/00 Ended Ended Ended Ended Ended
each period (unaudited) 1999 1998 1997 1996 1995
---------------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C> <C>
Class Z Class Z Class Z Class Z Class Z Class Z
---------------------------------------------------------------------------------------------------------------------------------
Net asset value, beginning of period $18.53 $16.85 $16.99 $15.04 $13.60 $12.24
---------------------------------------------------------------------------------------------------------------------------------
Income from Investment Operations:

Net investment income .06 .09 .04 .15 .09 .11
---------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on
investments, foreign currency and
futures (.32) 5.22 .91 3.57 2.93 2.42
---------------------------------------------------------------------------------------------------------------------------------
Total from investment
operations (.26) 5.31 .95 3.72 3.02 2.53
---------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income (.05) (.09) (.03) (.16) (.11) (.09)
---------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (1.00) (3.54) (1.06) (1.61) (1.47) (1.08)
---------------------------------------------------------------------------------------------------------------------------------
Total distributions (1.05) (3.63) (1.09) (1.77) (1.58) (1.17)
---------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $17.22 $18.53 $16.85 $16.99 $15.04 $13.60
---------------------------------------------------------------------------------------------------------------------------------
Total return (a) (1.41%) 33.4% 6.0% 25.0% 22.6% 20.8%
---------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net
assets .84%* .85% .84% .56% .57% .57%
---------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income to
average net assets .62%* .49% .30% .75% .53% .89%
---------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 35%* 34% 24% 32% 33% 29%
---------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $3,818 $3,921 $3,549 $3,681 $2,842 $2,399
</TABLE>

(a) Total return is not annualized for periods less than one year. Class A, B
and C shares are subject to sales loads, account fees and rule 12b-1 fees
that are not reflected in the total return.

* Annualized

----
21
<PAGE>

Notes

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----
22
<PAGE>

Notes

----
23
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You can get more information about the Fund's investments in the Fund's
semi-annual and annual reports to shareholders. The annual report contains a
discussion of the market conditions and investment strategies that significantly
affected the Fund's performance over its last fiscal year.

You may wish to read the Statement of Additional Information for more
information on the Fund and the securities in which it invests. The Statement of
Additional Information is incorporated into this prospectus by reference, which
means that it is considered to be part of this prospectus.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

You can review and copy information about the Fund by visiting the following
location, and you can obtain copies, upon payment of a duplicating fee by
electronic request at the E-mail address [email protected] or by writing the:

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn Fund (formerly Acorn Fund)

[LOGO OF LIBERTY FUNDS]

ALL-STAR.COLONIAL.CRABBE HUSON.NEWPORT.STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (c) 2000
One Financial Center, Boston, MA 02111-2621,1-800-426-3750
www.libertyfunds.com

---
24
<PAGE>

--------------------------------------------------------------------------------
LIBERTY ACORN INTERNATIONAL Prospectus, September 29, 2000
--------------------------------------------------------------------------------

Class A, B and C Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

<TABLE>
<CAPTION>
--------------------------------------------------------------------------
T A B L E O F C O N T E N T S

LIBERTY ACORN INTERNATIONAL 2
---------------------------
<S> <C>
Investment Goal..................................................... 2
Principal Investment Strategies..................................... 2
Principal Investment Risks.......................................... 2
Performance History................................................. 4
Your Expenses....................................................... 5

YOUR ACCOUNT 6
------------
How to Buy Shares................................................... 6
Sales Charges....................................................... 7
How to Exchange Shares.............................................. 11
How to Sell Shares.................................................. 11
Fund Policy on Trading of Fund Shares............................... 12
Distribution and Service Fees....................................... 13
Other Information About Your Account................................ 13

MANAGING THE FUND 17
-----------------
Investment Advisor.................................................. 17
Portfolio Managers.................................................. 17

OTHER INVESTMENT
STRATEGIES AND RISKS 19
--------------------
The Information Edge................................................ 19
Stock Strength Comes First.......................................... 19
Derivative Strategies............................................... 20
Temporary Defensive Strategies...................................... 20

FINANCIAL HIGHLIGHTS 21
--------------------
</TABLE>

Not FDIC May Lose Value
-----------------
Insured No Bank Guarantee
<PAGE>

Liberty Acorn International

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn International seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------

Liberty Acorn International invests primarily in stocks of non-U.S. small- and
medium-sized companies. The Fund generally invests in the stocks of companies
based outside the U.S. with capitalizations of less than $5 billion.

The Fund believes that smaller companies - particularly outside the U.S. - that
are not as well known by financial analysts may offer higher return potential
than the stocks of larger companies.

Liberty Acorn International typically looks for companies with:

. A strong business franchise that offers growth potential.
. Products and services that give the company a competitive advantage.
. A stock price the Fund's advisor believes is reasonable relative to the
assets and earning power of the company.

Liberty Acorn International is an international fund and invests the majority
(under normal market conditions, at least 75%) of its total assets in the stocks
of foreign companies based in developed markets (for example, Japan, Canada and
United Kingdom) and emerging markets (for example, Mexico, Brazil and Korea).

Additional strategies that are not principal investment strategies and the risks
associated with them are described later in this prospectus under "Other
Investment Strategies and Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

______
2
<PAGE>

Liberty Acorn International

such companies may suffer a decline in response. These price movements may
result from factors affecting individual companies, industries or the securities
market as a whole.

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of its assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

_____
3
<PAGE>

Liberty Acorn International

UNDERSTANDING PERFORMANCE

Calendar year total returns show the Fund's Class Z share performance for each
completed calendar year. They include the effects of Class Z expenses. Class A,
Class B and Class C shares are subject to sales charges, 12b-1 fees and
different expenses that are not reflected in the bar chart. If these amounts
were reflected, returns would be less than those shown.

Average annual total returns are measures of the Fund's Class Z performance over
the past one-year, five-year and life of the Fund periods. They include the
effects of Class Z expenses. The table shows for each class the Class Z
performance restated to reflect the effect of sales charges of the class.

The Fund's return are compared to Morgan Stanley's Europe, Australasia and Far
East Index (EAFE), an index of companies throughout the world in proportion to
stock market capitalizations, excluding the U.S. and Canada, and the EMI (world
ex-U.S.), Salomon Smith Barney's index of the bottom 20% of institutionally
investable capital of countries, selected by Salomon and excluding the U.S.
Unlike the Fund, indices are not investments, do not incur fees or expenses and
are not professionally managed. It is not possible to invest directly in
indices.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

Because Class A, Class B and Class C shares have not been offered for a full
calendar year, the information provided in the bar chart below shows changes in
the Fund's performance from year to year by illustrating the Fund's calendar
year total returns for its Class Z shares. Class Z shares are offered to certain
investors through a separate prospectus. The performance table following the bar
chart shows how the Fund's average annual returns for (1) the Class Z shares and
(2) the Class Z shares, restated to reflect the sales charges of the Class A,
Class B and Class C shares, respectively, compare with those of broad measures
of market performance for one year, five years and life of the Fund. The chart
and table are intended to illustrate some of the risks of investing in the Fund
by showing the changes in the Fund's Class Z performance. All returns include
the reinvestment of dividends and distributions. As with all mutual funds, past
performance does not predict the Fund's future performance.

Calendar Year Total Returns (Class Z)/(1)(2)/
--------------------------------------------------------------------------------
[BAR CHART]

Year Return
---- ------
1993 49.11%
1994 (3.80%)
1995 8.93%
1996 20.65%
1997 .19%
1998 15.43%
1999 79.19%

--------------------------------------------------------------------------------

For period shown in bar chart:
Best quarter: 4th quarter 1999, +41.63%
Worst quarter: 3rd quarter 1998,-16.05%

(1) Class Z shares are not offered through this prospectus, but Class A, Class
B and Class C shares would have substantially similar annual returns
because the shares are invested in the same portfolio of securities and
these returns differ only to the extent that the Classes do not have the
same expenses.

Average Annual Total Returns -- for periods ended December 31, 1999/(2)(3)/

<TABLE>
<CAPTION>
Life of the
Inception Date 1 Year 5 Years Fund
<S> <C> <C> <C> <C>
Class A 9/29/00 68.89% 20.75% 20.72%
-------------------------------------------------------------------------------
Class B 9/29/00 74.19% 22.01% 21.71%
-------------------------------------------------------------------------------
Class C 9/29/00 78.19% 22.19% 21.71%
-------------------------------------------------------------------------------
Class Z 9/23/92 79.19% 22.19% 21.71%
-------------------------------------------------------------------------------
EAFE N/A 26.96% 12.83% 13.50%
-------------------------------------------------------------------------------
EMI (world ex-U.S.) N/A 23.52% 7.21% 9.48%
</TABLE>

(2) The Fund's performance in 1999 was achieved during a period of unusual
market conditions that are unlikely to continue.

(3) Class A, Class B, and Class C are new classes of shares. Their performance
information includes returns of the Fund's Class Z shares (the oldest
existing Fund class) for periods prior to the inception of the newer
classes of shares. Class Z returns are not restated to reflect any
differences in expenses (such as Rule 12b-1 fees) between Class Z shares
and the newer classes of shares. If differences in expenses were reflected,
the returns for prior to the inception of the newer classes of shares would
be lower. Class Z shares were initially offered on September 23, 1992;
Class A, Class B and Class C shares were initially offered on September 29,
2000.

_____
4
<PAGE>

Liberty Acorn International

UNDERSTANDING EXPENSES

Sales Charges are paid directly by shareholders to Liberty Funds Distributor,
Inc., the Fund's distributor.

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, 12b-1 fees and administrative costs
including pricing and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

. assumes Class B shares convert to Class A shares after eight years

YOUR EXPENSES
--------------------------------------------------------------------------------

Expenses are one of several factors to consider before you invest in a mutual
fund. The tables below describe the fees and expenses you may pay when you buy,
hold and sell shares of the Fund.

Shareholder Fees/(4)/ (paid directly from your investment)

<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Maximum sales charge (load) on purchases (%)
(as a percentage of the offering price) 5.75 None None
------------------------------------------------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions (%) (as a percentage of the
lesser of purchase price or redemption price) 1.00/(5)/ 5.00 1.00
------------------------------------------------------------------------------------------------------
Redemption fee (6) (6) (6)
</TABLE>

(4) A $10 annual fee is deducted from accounts of less than $1,000 and paid to
the transfer agent.

(5) This charge applies only to certain Class A shares bought without an
initial sales charge that are sold within 18 months of purchase.

(6) There is a $7.50 charge for wiring sale proceeds to your bank.

Annual Fund Operating Expenses (deducted directly from fund assets)

<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Management Fees/(7)/(%) .81 .81 .81
------------------------------------------------------------------------------------------------------
Distribution and service (12b-1) fees (%) .35 1.00 1.00
------------------------------------------------------------------------------------------------------
Other expenses (%) .43 .43 .43
------------------------------------------------------------------------------------------------------
Total annual fund operating expenses (%) 1.59 2.24 2.24
</TABLE>

(7) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

Example Expenses (your actual costs may be higher or lower)
<TABLE>
<CAPTION>

Class 1 Year 3 Years 5 Years 10 Years
<S> <C> <C> <C> <C>
Class A: $ 727 $1,048 $1,391 $2,356
-----------------------------------------------------------------------------------------------
Class B: did not sell your shares $ 227 $ 700 $1,200 $2,411

sold all your shares at
the end of the period $ 727 $1,000 $1,400 $2,411
-----------------------------------------------------------------------------------------------
Class C: did not sell your shares $ 227 $ 700 $1,200 $2,575

sold all your shares at $ 327 $ 700 $1,200 $2,575
the end of the period
</TABLE>

______
5
<PAGE>

Your Account

INVESTMENT MINIMUMS

Initial Investment............................... $1,000
Subsequent Investments........................... $ 50
Automatic Investment Plan*....................... $ 50

Retirement Plans*................................ $ 25

* The initial investment minimum of $1,000 is waived on this plan.

HOW TO BUY SHARES
--------------------------------------------------------------------------------

Outlined below are the various options for buying shares:

Method Instructions

Through your Your financial advisor can help you establish
financial advisor your account and buy Fund shares on your behalf.
Your financial advisor may charge you fees for
executing the purchase for you.
--------------------------------------------------------------------------------
By check For new accounts, send a completed application
(new account) and check made payable to the Fund to the transfer
agent, Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
--------------------------------------------------------------------------------

By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your
quarterly statement, or send a letter of
instruction including your Fund name and account
number with a check made payable to the Fund to
Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
--------------------------------------------------------------------------------

By exchange You or your financial advisor may acquire shares by
exchanging shares you own in one fund for shares of
the same class of the Fund at no additional cost.
There may be an additional charge if exchanging
from a money market fund. To exchange by telephone,
call 1-800-422-3737.
--------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your
Fund account. To wire funds to your Fund account,
call 1-800-422-3737 to obtain a control number and
the wiring instructions.
--------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically trans-
transfer ferring money from your bank account to your Fund
account by calling 1-800-422-3737. Electronic funds
transfers may take up to two business days to
settle and be considered in "good form." You must
set up this feature prior to your telephone
request. Be sure to complete the appropriate
section of the application.
--------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your Fund
account. You can select a pre-authorized amount to
be sent via electronic funds transfer. Be sure to
complete the appropriate section of the application
for this feature.
--------------------------------------------------------------------------------

Your Account

CHOOSING A SHARE CLASS

The Fund offers three classes of shares in this prospectus -- Class A, B and C.
Each share class has its own sales charge and expense structure. Determining
which share class is best for you depends on the dollar amount you are investing
and the number of years for which you are willing to invest. If your financial
advisor firm does not participate in the Class B discount program, purchases of
$250,000 or more must be for Class A or Class C shares only. Purchases of $1
million or more can be made only in Class A shares. Based on your personal
situation, your financial advisor can help you decide which class of shares
makes the most sense for you.

Class A Sales Charges

<TABLE>
<CAPTION>
% of offering
As a % of price
the public As a % retained by
offering of your financial
Amount of purchase price investment advisor firm
<S> <C> <C> <C>
Less than $50,000 5.75 6.10 5.00
---------------------------------------------------------------------------------------------------------
$50,000 to less than $100,000 4.50 4.71 3.75
---------------------------------------------------------------------------------------------------------
$100,000 to less than $250,000 3.50 3.63 2.75
---------------------------------------------------------------------------------------------------------
$250,000 to less than $500,000 2.50 2.56 2.00
---------------------------------------------------------------------------------------------------------
$500,000 to less than $1,000,000 2.00 2.04 1.75
---------------------------------------------------------------------------------------------------------
$1,000,000 or more 0.00 0.00 0.00
</TABLE>

Class A shares bought without an initial sales charge in accounts aggregating $1
million to $25 million at the time of purchase are subject to a 1.00% CDSC if
the shares are sold within 18 months of the time of purchase. Subsequent Class A
share purchases that bring your account value above $1 million are subject to a
CDSC if redeemed within 18 months of the date of purchase. The 18-month
period begins on the first day of the month following each purchase. The CDSC
does not apply to retirement plans purchasing shares through a fee-based
program.

For Class A share purchases of $1 million or more, financial advisors receive a
commission from the distributor as follows:

Purchases Over $1 Million

Amount purchased Commission %

First $3 million 1.00
-------------------------------------------------------------------------------

$3 million to less than $5 million 0.80
-------------------------------------------------------------------------------

$5 million to less than $25 million 0.50
-------------------------------------------------------------------------------

$25 million or more 0.25

The commission to financial advisors for Class A share purchases of $25 million
or more is paid over 12 months but only to the extent the shares remain
outstanding.

For Class A share purchases by participants in certain group retirement plans
offered through a fee-based program, financial advisors receive a 1.00%
commission from the distributor on all purchases of less than $3 million.

_____
7
<PAGE>

Your Account

UNDERSTANDING CONTINGENT DEFERRED SALES CHARGES (CDSC)

Class B shares Your purchases of Class B shares are at Class B shares' net asset
value. Class B shares have no front-end sales charge, but they do carry a CDSC
that is imposed only on shares sold prior to the completion of the periods shown
in the charts below. The CDSC generally declines each year and eventually
disappears over time. The distributor pays the financial advisor firm an up-
front commission on sales of Class B shares as depicted in the charts below.

Purchases of less than $250,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 5.00
--------------------------------------------------------------------------------
Through second year 4.00
--------------------------------------------------------------------------------
Through third year 3.00
--------------------------------------------------------------------------------
Through fourth year 3.00
--------------------------------------------------------------------------------
Through fifth year 2.00
--------------------------------------------------------------------------------
Through sixth year 1.00
--------------------------------------------------------------------------------
Longer than six years None

Commission to financial advisors is 5.00%.

Automatic conversion to Class A shares is eight years after purchase.

_____
8
<PAGE>

Your Account

Purchases of $250,000 to less than $500,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 3.00
-------------------------------------------------------------------------------
Through second year 2.00
-------------------------------------------------------------------------------
Through third year 1.00
-------------------------------------------------------------------------------
Longer than three years 0.00

Commission to financial advisors is 2.50%.

Automatic conversion to Class A shares is four years after purchase.

Purchases of $500,000 to less than $1 million:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Commission to financial advisors is 1.75%.

Automatic conversion to Class A shares is three years after purchase.

_____
9
<PAGE>

Your Account

Class C Sales Charges

Years after purchase % deducted when shares are sold

Through one year 1.00
--------------------------------------------------------------------------------

Longer than one year 0.00

_____
10
<PAGE>

Your Account

_____
11
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions

Through your You may call your financial advisor to place your sell
financial advisor order. To receive the current trading day's price, your
financial advisor firm must receive your request prior
to the close of the NYSE, usually 4:00 p.m. Eastern
time.
-------------------------------------------------------------------------------
By exchange You or your financial advisor may sell shares by
exchanging from the Fund into the same share class of
another Liberty fund at no additional cost. To exchange
by telephone, call 1-800-422-3737.
--------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by
telephone and request that a check be sent to your
address of record by calling 1-800-422-3737, unless you
have notified the Fund of an address change within the
previous 30 days. The dollar limit for telephone sales
is $100,000 in a 30-day period. You do not need to set
up this feature in advance of your call. Certain
restrictions apply to retirement accounts. For details,
call 1-800-345-6611.
--------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock
power form along with any certificates to be sold to the
address below. In your letter of instruction, note your
Fund's name, share class, account number, and the dollar
value or number of shares you wish to sell. All account
owners must sign the letter, and signatures must be
guaranteed by either a bank, a member firm of a national
stock exchange or another eligible guarantor
institution. Additional documentation is required for
sales by corporations, agents, fiduciaries, surviving
joint owners and individual retirement account owners.
For details, call 1-800-345-6611.

By systematic You may automatically sell a specified dollar amount
withdrawal plan or percentage on a monthly, quarterly or semi-annual
basis if your account balance is at least $5,000 and
have the proceeds sent to you. This feature is not
available if you hold your shares in certificate form.
Be sure to complete the appropriate section of the
account application for this feature.
-------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may
take up to two business days to be received by your
bank. You must set up this feature prior to your
request. Be sure to complete the appropriate section of
the account application for this feature.

FUND POLICY ON TRADING OF FUND SHARES
--------------------------------------------------------------------------------
The Fund does not permit short-term or excessive trading. Excessive purchases,
redemptions or exchanges of Fund shares disrupt portfolio management and drive
Fund expenses higher. In order to promote the best interests of the Fund, the
Fund reserves the right to reject any purchase order or exchange request,
particularly from market timers or investors who, in the advisor's opinion, have
a pattern of short-term or excessive trading or whose trading has been or may be
disruptive to the Fund. The fund into which you would like to exchange also may
reject your request.

____
12
<PAGE>

Your Account

DISTRIBUTION AND SERVICE FEES
--------------------------------------------------------------------------------
The Fund has adopted a plan under Rule 12b-1 that permits it to pay the Fund's
distribution, marketing and other fees to support the sale and distribution of
Class A, B and C shares and certain services provided to you by your financial
advisor. The annual service fee may equal up to 0.25% for Class A, Class B and
Class C shares. The annual distribution fee may equal up to 0.10% for Class A
shares and 0.75% for Class B and Class C shares. Distribution and service fees
are paid out of the assets of these classes. Over time, these fees may reduce
the return on your investment and may cost you more than paying other types of
sales charges. Class B shares automatically convert to Class A shares after a
certain number of years, eliminating a portion of the distribution fee upon
conversion. Conversion may occur three, four or eight years after purchase,
depending on the program you purchased your shares under. See "Your Account;
Sales Charge" for the conversion schedule applicable to Class B shares.

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------
How the Fund's Share Price is Determined The price of each class of the Fund's
shares is based on its net asset value. The net asset value is determined at the
close of regular trading on the NYSE, usually 4:00 p.m. Eastern time, on each
business day that the NYSE is open (typically Monday through Friday).

Account Fees If your account value falls below $1,000 (other than as a result of
depreciation in share value) you may be subject to an annual account fee of $10.
This fee is deducted from the account in June each year. Approximately 60 days
prior to the fee date, the Fund's transfer agent will send you written
notification of the upcoming fee. If

_____
13
<PAGE>

Your Account

you add money to your account and bring the value above $1,000 prior to the fee
date, the fee will not be deducted.

_____
14
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

DIVIDENDS, DISTRIBUTIONS, AND TAXES The Fund has the potential to make the
following distributions:

Types of Distributions

DISTRIBUTION OPTIONS The Fund distributes dividends in June and December and any
capital gains (including short-term capital gains) at least annually. You can
choose one of the options listed in the table below for these distributions when
you open your account. To change your distribution option call 1-800-345-6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
-------------------------------------------------------------------------------
Reinvest all distributions in shares of another Liberty fund
-------------------------------------------------------------------------------

Receive dividends in cash (see options below) and reinvest capital gains
-------------------------------------------------------------------------------
Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

_____
15
<PAGE>

Your Account

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

_____
16
<PAGE>

Managing the Fund

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.81% of the Fund's
average daily net assets. Liberty WAM also receives an administrative services
fee from the Fund at the annual rate of .05% of the Fund's average daily net
assets.

Leah J. Zell
Lead portfolio manager

Margaret M. Forster
Co-portfolio manager

____
17
<PAGE>

Managing the Fund

of WAM from January 1999 to September 29, 2000. Prior to that, Ms. Forster was a
professor of finance at Northwestern and Ohio State Universities, and an
economist with the International Monetary Fund. She is a CFA. Her degrees
include a BS from Universidade de Sao Paulo, Escola Politecnica, Brazil, and an
MBA, MS and PhD from Cornell University.

_____
18
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

The Fund's principal investment strategies and risks are described under
"Liberty Acorn International - Principal Investment Strategies" and "Liberty
Acorn International - Principal Investment Risks." In seeking to meet its
investment goal, the Fund may also invest in other securities and use certain
other investment techniques. These securities and investment techniques offer
opportunities and carry various risks.

THE INFORMATION EDGE
--------------------------------------------------------------------------------

The Fund invests in entrepreneurially managed smaller and mid-sized companies
that it believes are not as well known by financial analysts and whose
domination of a niche creates the opportunity for superior earnings-growth
potential. Liberty WAM may identify what it believes are important economic,
social or technological trends (for example, the growth of out-sourcing as a
business strategy, or the productivity gains from the increasing use of
technology) and try to identify companies it thinks will benefit from those
trends.

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
---------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt
. innovative marketing . adequate working . reasonable stock
. managerial skill capital price relative to
. market niche . conservative growth potential
. good earnings accounting practices . valuable assets
. strong demand for . adequate profit
product margin

The realization of this A strong balance sheet Once Liberty WAM
growth potential would gives management greater uncovers an attractive
likely produce superior flexibility to pursue company, it iden-
performance that is strategic objectives and tifies a price that
sustainable over time. is essential to maintain- it believes would
ing a competitive advant- also make the stock
age. a good value.
---------------------------------------------------------------------------------
</TABLE>

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------
Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty WAM
analysts talk to top management, vendors, suppliers and competitors, whenever
possible.

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

_____
19
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------

The Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money than the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------

At times, Liberty WAM may determine that adverse market conditions make it
desirable to temporarily suspend the Fund's normal investment activities. During
such times, the Fund may, but is not required to, invest in cash or high-
quality, short-term debt securities, without limit. Taking a temporary defensive
position may prevent the Fund from achieving its investment goal.

_____
20
<PAGE>

Financial Highlights

The financial highlights tables are intended to help you understand the Fund's
financial performance. Because Class A, Class B and Class C shares are new
classes of shares, information is shown for the Fund's Class Z shares for the
last five fiscal years and for the six months ended June 30, 2000. The Fund's
fiscal year runs from January 1 to December 31. Class Z shares are offered to
certain investors through separate prospectuses. Certain information reflects
financial results for a single Fund share. The total returns in the table
represent the rate that you would have earned (or lost) on the Fund (assuming
reinvestment of all dividends and distributions). The information with respect
to the six month period ended June 30, 2000 is unaudited. The information with
respect to the last five years is audited. For periods up to and including the
year ended 1999, this information has been derived from the Fund's financial
statements which have been audited by Ernst & Young LLP, independent auditors
whose report, along with the Fund's audited financial statements, is included in
the Fund's annual report. You can request a free annual report by calling
1-800-426-3750.

Liberty Acorn International

Year Year Year Year Year
For a share outstanding throughout Six months ended ended ended ended ended
each period ended 6/30/00 12/31/99 12/31/98 12/31/97 12/31/96 12/31/95
-------------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C> <C>
Class Z Class Z Class Z Class Z Class Z Class Z
-------------------------------------------------------------------------------------------------------------------------------
Net asset value, beginning of period $ 35.33 $ 20.82 $ 18.39 $ 19.61 $ 16.59 $ 15.24
-------------------------------------------------------------------------------------------------------------------------------
Income from Investment Operations:

Net investment income -- .83 .17 .40 .13 .16
-------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain (loss)
on investments, foreign currency and
futures (1.34) 15.45 2.68 (.34) 3.29 1.20
-------------------------------------------------------------------------------------------------------------------------------
Total from investment
operations (1.34) 16.28 2.85 .06 3.42 1.36
-------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income (.66) (.22) (.15) (.38) (.12) --
-------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.51) (1.55) (.27) (.90) (.28) (.01)
-------------------------------------------------------------------------------------------------------------------------------
Total distributions (1.17) (1.77) (.42) (1.28) (.40) (.01)
-------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $ 32.82 $ 35.33 $ 20.82 $ 18.39 $ 19.61 $ 16.59
-------------------------------------------------------------------------------------------------------------------------------
Total return (a) (3.8%) 79.2% 15.4% 0.2% 20.7% 8.9%
-------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net
assets 1.06%* 1.11% 1.12% 1.19% 1.17% 1.22%
-------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income to
average net assets .01%* .12% .86% .58% .51% .90%
-------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 76%* 46% 37% 39% 34% 26%
-------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 2,984 $ 2,868 $ 1,725 $ 1,623 $ 1,773 $ 1,276
</TABLE>

(a) Total return is not annualized for periods less than one year. Class A, B
and C shares are subject to sales loads, account fees and rule 12b-1 fees
that are not reflected in the total return.

*Annualized

_____
21
<PAGE>

Notes

________________________________________________________________________________

____
22
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn International (formerly Acorn International)

[LOGO OF LIBERTY FUNDS]

---
23
<PAGE>

----------------------------------------------------------------------------

LIBERTY ACORN USA Prospectus, September 29, 2000
----------------------------------------------------------------------------

Class A, B and C Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
T A B L E O F C O N T E N T S
<S> <C>
LIBERTY ACORN USA 2
-----------------
Investment Goal............................................................. 2
Principal Investment Strategies............................................. 2
Principal Investment Risks.................................................. 2
Performance History......................................................... 4
Your Expenses............................................................... 5

YOUR ACCOUNT 6
------------
How to Buy Shares........................................................... 6
Sales Charges............................................................... 7
How to Exchange Shares...................................................... 11
How to Sell Shares.......................................................... 11
Fund Policy on Trading of Fund Shares....................................... 12
Distribution and Service Fees............................................... 13
Other Information About Your Account........................................ 13

MANAGING THE FUND 17
-----------------
Investment Advisor.......................................................... 17
Portfolio Manager........................................................... 17

OTHER INVESTMENT
STRATEGIES AND RISKS 18
--------------------
The Information Edge........................................................ 18
Stock Strength Comes First.................................................. 18
Derivative Strategies....................................................... 19
Temporary Defensive Strategies.............................................. 19

FINANCIAL HIGHLIGHTS 20
--------------------
</TABLE>

Not FDIC May Lose Value
------------------
Insured No Bank Guarantee

<PAGE>

-----------------------------------------------------------------------------
Liberty Acorn USA
-----------------------------------------------------------------------------

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn USA seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------

Liberty Acorn USA invests primarily in stocks of small-and medium-sized U.S.
companies. The Fund generally invests in the stocks of U.S. companies with
capitalizations of less than $2 billion.

The Fund believes that these smaller companies, which are not as well known by
financial analysts, may offer higher return potential than the stocks of larger
companies. Liberty, Acorn USA typically looks for companies with:

The Fund generally invests substantially all of its assets in U.S companies and,
under normal market conditions, will invest at least 65% of its assets in U.S.
companies.

Additional strategies that are not principal investment strategies and the risks
associated with them are described later in this prospectus under "Other
Investment Strategies and Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are
many circumstances (including additional risks that are not described here)
which could prevent the Fund from achieving its investment goal. You may lose
money by investing in the Fund.

Liberty Acorn USA

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times, the Fund may have a large portion of its assets invested in a
particular sector. An example of a sector in which the Fund may sometimes have a
significant portion of its assets invested is technology. Technology companies
may be significantly affected by falling prices and profits, and intense
competition. In addition, the rate of technological change for technology
companies is generally higher than for other companies, often requiring
extensive and sustained investment in research and development, and exposing
such companies to the risk of rapid product obsolescence. The price of many
technology stocks has risen based on projections of future earnings and company
growth. If a company does not perform as expected, the price of the stock could
decline significantly. Many technology companies are currently operating at a
loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

_____
3
<PAGE>

Liberty Acorn USA

UNDERSTANDING PERFORMANCE

Average annual total returns are measures of the Fund's Class Z performance over
the past one-year, three-year and life of the Fund periods. They include the
effects of Class Z expenses. The table shows for each class the Class Z
performance restated to reflect the effect of sales charges of each class.

The Fund's return is compared to the Russell 2000 Index. The Russell 2000 Index
is a market-weighted index of 2000 small companies formed by taking the largest
3000 companies and eliminating the largest 1000 of those companies. Unlike the
Fund, an index is not an investment, does not incur fees or expenses and is not
professionally managed. It is not possible to invest directly in an index.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

Because Class A, Class B and Class C shares have not been offered for a full
calendar year, the information provided in the bar chart below shows changes in
the Fund's performance from year to year by illustrating the Fund's calendar
year total returns for its Class Z shares. Class Z shares are offered to
certain investors through a separate prospectus. The performance table
following the bar chart shows how the Fund's average annual returns for (1) the
Class Z shares and (2) the Class Z shares, restated to reflect the sales charges
of the Class A, Class B and Class C shares, respectively, compare with those of
broad measures of market performance for one year, three years and life of the
Fund. The chart and table are intended to illustrate some of the risks of
investing in the Fund by showing the changes in the Fund's Class Z performance.
All returns include the reinvestment of dividends and distributions. As with all
mutual funds, past performance does not predict the Fund's future
performance.

Calendar Year Total Returns (Class Z)/(1)/

-------------------------------------------------------------------------------
[BAR CHART]

Year Returns
---- -------
1997 32.30%
1998 5.79%
1999 23.02%

-------------------------------------------------------------------------------

For period shown in bar chart:
Best quarter: 4th quarter 1999, +18.93%
Worst quarter: 3rd quarter 1998, -19.25%

(1) Class Z shares are not offered through this prospectus, but Class A, Class
B and Class C shares would have substantially similar annual returns
because the shares are invested in the same portfolio of securities and
these returns differ only to the extent that the classes do not have the
same expenses.

Average Annual Total Returns -- for periods ended December 31, 1999 /(2)/

<TABLE>
<CAPTION>
Life of
the
Inception Date 1 Year 3 Years Fund
<S> <C> <C> <C> <C>
Class A 9/29/00 15.95% 17.51% 21.10%
--------------------------------------------------------------------------------
Class B 9/29/00 18.02% 19.16% 22.72%
--------------------------------------------------------------------------------
Class C 9/29/00 22.02% 19.86% 23.28%
--------------------------------------------------------------------------------
Class Z 9/4/96 23.02% 19.86% 23.28%
--------------------------------------------------------------------------------
Russell 2000 N/A 21.26% 13.08% 14.65%
</TABLE>

(2) Class A, Class B, and Class C are new classes of shares. Their performance
information includes returns of the Fund's Class Z shares (the oldest
existing Fund class) for periods prior to the inception of the newer
classes of shares. Class Z returns are not restated to reflect any
differences in expenses (such as Rule 12b-1 fees) between Class Z shares
and the newer classes of shares. If differences in expenses were reflected,
the returns for prior to the inception of the newer classes of shares would
be lower. Class Z shares were initially offered on September 4, 1996; Class
A, Class B and Class C shares were initially offered on September 29,
2000.

_____
4

<PAGE>

Liberty Acorn USA

UNDERSTANDING EXPENSES

Sales Charges are paid directly by shareholders to Liberty Funds Distributor,
Inc., the Fund's distributor.

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, 12b-1 fees and administrative costs
including pricing and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

. assumes Class B shares convert to Class A shares after eight years

Shareholder Fees/(3)/ (paid directly from your investment)

<TABLE>
<CAPTION>
CLASS A Class B Class C
<S> <C> <C> <C>
Maximum sales charge (load) on purchases (%)
(as a percentage of the offering price) 5.75 None None
---------------------------------------------------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions (%) (as a percentage of the
lesser of purchase price or redemption price) 1.00/(4)/ 5.00 1.00
---------------------------------------------------------------------------------------------------------
Redemption fee (5) (5) (5)
</TABLE>

(3) A $10 annual fee is deducted from accounts of less than $1,000 and paid to
the transfer agent.
(4) This charge applies only to certain Class A shares bought without an
initial sales charge that are sold within 18 months of purchase.
(5) There is a $7.50 charge for wiring sale proceeds to your bank.

Annual Fund Operating Expenses (deducted directly from fund assets)

<TABLE>
<CAPTION>
CLASS A Class B Class C
<S> <C> <C> <C>
Management fees/(6)/(%) .93 .93 .93
-------------------------------------------------------------------------------------------------
Distribution and service (12b-1) fees (%) .35 1.00 1.00
-------------------------------------------------------------------------------------------------
Other expenses (%) .37 .37 .37
-------------------------------------------------------------------------------------------------
Total annual fund operating expenses (%) 1.65 2.30 2.30
</TABLE>

(6) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

Example Expenses (your actual costs may be higher or lower)

Class 1 Year 3 Years 5 Years 10 Years

Class A: $ 733 $1,065 $1,420 $2,417
--------------------------------------------------------------------------------
Class B: did not sell your shares $ 233 $ 718 $1,230 $2,473

sold all your shares at
the end of the period $ 733 $1,018 $1,430 $2,473
--------------------------------------------------------------------------------
Class C: did not sell your shares $ 233 $ 718 $1,230 $2,636

sold all your shares at
the end of the period $ 333 $ 718 $1,230 $2,636

_____
5
<PAGE>

Your Account

INVESTMENT MINIMUMS

Initial Investment............................ $1,000
Subsequent Investments........................ $ 50

Automatic Investment Plan*.................... $ 50
Retirement Plans*............................. $ 25

* The initial investment minimum of $ 1,000 is waived on this plan.

HOW TO BUY SHARES
--------------------------------------------------------------------------------

Method Instructions

Through your Your financial advisor can help you establish your
financial advisor account and buy Fund shares on your behalf. Your
financial advisor may charge you fees for executing the
purchase for you.
--------------------------------------------------------------------------------
By check For new accounts, send a completed application and
(new account) check made payable to the Fund to the transfer agent,
Liberty Funds Services, Inc., P.O. Box 1722, Boston, MA
02105-1722.
--------------------------------------------------------------------------------

By exchange You or your financial advisor may acquire shares by
exchanging shares you own in one fund for shares of the
same class of the Fund at no additional cost. There may
be an additional charge if exchanging from a money
market fund. To exchange by telephone, call 1-800-422-
3737.
--------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your bank
account to your Fund account. To wire funds to your
Fund account, call 1-800-422-3737 to obtain a control
number and the wiring instructions.
--------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically transferring
transfer money from your bank account to your Fund account by
calling 1-800-422-3737. Electronic funds transfers may
take up to two business days to settle and be
considered in "good form." You must set up this feature
prior to your telephone request. Be sure to complete
the appropriate section of the application.
--------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your Fund
account. You can select a pre-authorized amount to be
sent via electronic funds transfer. Be sure to complete
the appropriate section of the application for this
feature.
--------------------------------------------------------------------------------

Your Account

CHOOSING A SHARE CLASS

The Fund offers three classes of shares in this prospectus -- CLASS A, B and C.
Each share class has its own sales charge and expense structure. Determining
which share class is best for you depends on the dollar amount you are investing
and the number of years for which you are willing to invest. If your financial
advisor firm does not participate in the Class B discount program, purchases of
$250,000 or more must be for Class A or Class C shares only. Purchases of $1
million or more can be made only in Class A shares. Based on your personal
situation, your financial advisor can help you decide which class of shares
makes the most sense for you.

Class A Shares Your purchases of Class A shares generally are at the public
offering price. This price includes a sales charge that is based on the amount
of your initial investment when you open your account. A portion of the sales
charge is the commission paid to the financial advisor firm on the sale of Class
A shares. The sales charge you pay on additional investments is based on the
total amount of your purchase and the current value of your account. The amount
of the sales charge differs depending on the amount you invest as shown in the
table below.

Class A Sales Charges

<TABLE>
<CAPTION>
% of offering
As a % of price
the public As a % retained by
offering of your financial
Amount of purchase price investment advisor firm
<S> <C> <C> <C>
Less than $50,000 5.75 6.10 5.00
--------------------------------------------------------------------------------
$50,000 to less than $100,000 4.50 4.71 3.75
--------------------------------------------------------------------------------
$100,000 to less than $250,000 3.50 3.63 2.75
--------------------------------------------------------------------------------
$250,000 to less than $500,000 2.50 2.56 2.00
--------------------------------------------------------------------------------
$500,000 to less than $1,000,000 2.00 2.04 1.75
--------------------------------------------------------------------------------
$1,000,000 or more 0.00 0.00 0.00
--------------------------------------------------------------------------------
</TABLE>

Class A shares bought without an initial sales charge in accounts aggregating $1
million to $25 million at the time of purchase are subject to a 1.00% CDSC if
the shares are sold within 18 months of the time of purchase. Subsequent Class A
share purchases that bring your account value above $1 million are subject to a
CDSC if redeemed within 18 months of the date of purchase. The 18-month period
begins on the first day of the month following each purchase. The CDSC does not
apply to retirement plans purchasing shares through a fee-based program.

For Class A share purchases of $1 million or more, financial advisors receive a
commission from the distributor as follows:

Purchases Over $1 Million

Amount purchased Commission %

First $3 million 1.00
--------------------------------------------------------------------------------

$3 million to less than $5 million 0.80
--------------------------------------------------------------------------------
$5 million to less than $25 million 0.50
--------------------------------------------------------------------------------
$25 million or more 0.25

The commission to financial advisors for Class A share purchases of $25 million
or more is paid over 12 months but only to the extent the shares remain
outstanding.

_____
7
<PAGE>

Your Account

UNDERSTANDING CONTINGENT DEFERRED SALES CHARGES (CDSC)

Class B Shares Your purchases of Class B shares are at Class B shares' net
asset value. Class B shares have no front-end sales charge, but they do carry a
CDSC that is imposed only on shares sold prior to the completion of the periods
shown in the charts below. The CDSC generally declines each year and eventually
disappears over time. The distributor pays the financial advisor firm an up-
front commission on sales of Class B shares as depicted in the charts below.

Purchases of less than $250,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Commission to financial advisors is 5.00%.
Automatic conversion to Class A shares is eight years after purchase.

_____
8
<PAGE>

Your Account

Purchases of $250,000 to less than $500,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 3.00
--------------------------------------------------------------------------------
Through second year 2.00
--------------------------------------------------------------------------------
Through third year 1.00
--------------------------------------------------------------------------------
Longer than three years 0.00

Commission to financial advisors is 2.50%.
Automatic conversion to Class A shares is four years after purchase.

Purchases of $500,000 to less than $1 million:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Commission to financial advisors is 1.75%.
Automatic conversion to Class A shares is three years after purchase.

______
9
<PAGE>

Your Account

Class C Shares Similar to Class B shares, your purchases of Class C shares are
at Class C's net asset value. Although Class C shares have no front-end sales
charge, they carry a CDSC of 1.00% that is applied to shares sold within the
first year after they are purchased. After holding shares for one year, you may
sell them at any time without paying a CDSC. The distributor pays the financial
advisor firm an up-front commission of 1.00% on sales of Class C shares.

Class C Sales Charges

Years After Purchase % deducted when shares are sold

Through one year 1.00
--------------------------------------------------------------------------------
Longer than one year 0.00

____
10
<PAGE>

Your Account

HOW TO EXCHANGE SHARES
-------------------------------------------------------------------------------

You may exchange your shares for shares of the same share class of another fund
distributed by Liberty Funds Distributor, Inc. at net asset value. If your
shares are subject to a CDSC, you will not be charged a CDSC upon the exchange.
However, when you sell the shares acquired through the exchange, the shares sold
may be subject to a CDSC, depending upon when you originally purchased the
shares you exchanged. For purposes of computing the CDSC, the length of time you
have owned your shares will be computed from the date of your original purchase
and the applicable CDSC will be the CDSC of the original fund. Unless your
account is part of a tax-deferred retirement plan, an exchange is a taxable
event. Therefore, you may realize a gain or a loss for tax purposes. The Fund
may terminate your exchange privilege if the advisor determines that your
exchange activity is likely to adversely impact its ability to manage the Fund.
To exchange by telephone, call 1-800-422-3737.

HOW TO SELL SHARES
--------------------------------------------------------------------------------

Your financial advisor can help you determine if and when you should sell your
shares. You may sell shares of the Fund on any regular business day that the New
York Stock Exchange (NYSE) is open.

_____
11
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions

Through your You may call your financial advisor to place your sell
financial advisor order. To receive the current trading day's price, your
financial advisor firm must receive your request prior
to the close of the NYSE, usually 4:00 p.m. Eastern
time.
--------------------------------------------------------------------------------
By exchange You or your financial advisor may sell shares by
exchanging from the Fund into the same share class of
another Liberty fund at no additional cost. To exchange
by telephone, call 1-800-422-3737.
--------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by
telephone and request that a check be sent to your
address of record by calling 1-800-422-3737, unless you
have notified the Fund of an address change within the
previous 30 days. The dollar limit for telephone sales
is $100,000 in a 30-day period. You do not need to set
up this feature in advance of your call. Certain
restrictions apply to retirement accounts. For details,
call 1-800-345-6611.
--------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock
power form along with any share certificates to be sold
to the address below. In your letter of instruction,
note your Fund's name, share class, account number, and
the dollar value or number of shares you wish to sell.
All account owners must sign the letter, and signatures
must be guaranteed by either a bank, a member firm of a
national stock exchange or another eligible guarantor
institution. Additional documentation is required for
sales by corporations, agents, fiduciaries, surviving
joint owners and individual retirement account owners.
For details, call 1-800-345-6611.

By systematic You may automatically sell a specified dollar amount
withdrawal plan or percentage on a monthly, quarterly or semi-annual
basis if your account balance is at least $5,000 and
have the proceeds sent to you. This feature is not
available if you hold your shares in certificate form.
Be sure to complete the appropriate section of the
account application for this feature.
--------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may
take up to two business days to be received by your
bank. You must set up this feature prior to your
request. Be sure to complete the appropriate section of
the account application for this feature.

FUND POLICY ON TRADING OF FUND SHARES
--------------------------------------------------------------------------------

___
12
<PAGE>

Your Account

DISTRIBUTION AND SERVICE FEES
--------------------------------------------------------------------------------

The Fund has adopted a plan under Rule 12b-1 that permits it to pay the Fund's
distribution, marketing and other fees to support the sale and distribution of
Class A, B and C shares and certain services provided to you by your financial
advisor. The annual service fee may equal up to 0.25% for Class A, Class B and
Class C shares. The annual distribution fee may equal up to 0.10% for Class A
shares and 0.75% for Class B and Class C shares. Distribution and service fees
are paid out of the assets of these classes. Over time, these fees may reduce
the return on your investment and may cost you more than paying other types of
sales charges. Class B shares automatically convert to Class A shares after a
certain number of years, eliminating a portion of the distribution fee upon
conversion. Conversion may occur three, four or eight years after purchase,
depending on the program you purchased your shares under. See "Your Account:
Sales Charge" for the conversion schedule applicable to Class B shares.

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------

___
13
<PAGE>

Your Account

____
14
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from
securities held by the Fund, net of expenses
incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of
securities held for more than 12 months and net
short-term capital gains, which are gains on sales
of securities held for a 12-month period or less.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Receive dividends in cash (see options below) and reinvest capital gains
--------------------------------------------------------------------------------
Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distribution of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

____
15
<PAGE>

Your Account

Tax Consequences Regardless of whether you receive your distributions in cash
or reinvest them in additional Fund shares, all Fund distributions are subject
to federal income tax. Depending on the state where you live, distributions may
also be subject to state and local income taxes.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on federal, state, local or other applicable tax
laws.

____
16
<PAGE>

Managing the Fund

INVESTMENT ADVISOR
--------------------------------------------------------------------------------

Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset Management,
L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago, Illinois
60606, is the Fund's investment advisor. Liberty WAM and its predecessor have
managed mutual funds, including the Fund, since 1992. In its duties as
investment advisor, Liberty WAM runs the Fund's day-to-day business, including
placing all orders for the purchase and sale of the Fund's portfolio securities.
As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.93% of the Fund's
average daily net assets. Liberty WAM also receives an administrative services
fee from the Fund at the annual rate of .05% of the Fund's average daily net
assets.

PORTFOLIO MANAGER
--------------------------------------------------------------------------------

Liberty WAM uses a team to manage the Fund. Team members share responsibility
for providing ideas, information, and knowledge in managing the Fund, and each
team member has one or more particular areas of expertise. The portfolio
managers are responsible for making daily investment decisions, and utilize the
management team's input and advice when making buy and sell determinations.

Robert A. Mohn
Lead portfolio manager

____
17
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

The Fund's principal investment strategies and risks are described under
"Liberty Acorn USA - Principal Investment Strategies" and "Liberty Acorn USA -
Principal Investment Risks." In seeking to meet its investment goal, the Fund
may also invest in other securities and use certain other investment techniques.
These securities and investment techniques offer opportunities and carry various
risks.

THE INFORMATION EDGE
--------------------------------------------------------------------------------

In making investments for the Fund, Liberty WAM relies primarily on independent,
internally generated research to uncover companies that may be less well known
than the more popular names. To find these companies, Liberty WAM compares
growth potential, financial strength and fundamental value among companies.
Liberty WAM may identify what it believes are important economic, social or
technological trends (for example, the growth of out-sourcing as a business
strategy, or the productivity gains from the increasing use of technology) and
try to identify companies it thinks will benefit from these trends.

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock price
. innovative marketing . adequate working relative to growth
. managerial skill capital potential
. market niche . conservative . valuable assets
. good earnings accounting practices
prospects . adequate profit margin
. strong demand for
product

Other Investment Strategies and Risks

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------

Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty WAM
analysts talk to top management, vendors, suppliers and competitors, whenever
possible.

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

____
18
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------

____
19
<PAGE>

Financial Highlights

The financial highlights tables are intended to help you understand the Fund's
financial performance. Because Class A, Class B and Class C shares are new
classes of shares, information is shown for the Fund's Class Z shares since
inception. The Fund's fiscal year runs from January 1 to December 31. Class Z
shares are offered to certain investors through separate prospectuses. Certain
information reflects financial results for a single Fund share. The total
returns in the table represent the rate that you would have earned (or lost) on
an investment in the Fund (assuming reinvestment of all dividends and
distributions). The information with respect to the six month period ended June
30, 2000 is unaudited. The information for the three years ended December 31,
1999 and the period ended December 31, 1996 is audited. For periods up to and
including the year ended 1999, this information has been derived from the Fund's
audited financial statements which have been audited by Ernst & Young LLP,
independent auditors, whose report, along with the Fund's financial statements,
is included in the Fund's annual report. You can request a free annual report by
calling 1-800-426-3750.

Liberty Acorn USA

<TABLE>
<CAPTION>
Six months ended
For a share outstanding throughout 6/30/00 Year Ended Year Ended Year Ended Inception 9/4/96
each period (unaudited) 12/31/99 12/31/98 12/31/97 Through 12/31/96
---------------------------------------------------------------------------------------------------------------------------------
Class Z Class Z Class Z Class Z Class Z
---------------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C>
Net asset value, beginning of period $16.75 $ 14.80 $ 15.12 $ 11.65 $ 10.00
---------------------------------------------------------------------------------------------------------------------------------

Income from Investment
Operations:

Net investment loss (a) (.02) -- (.07) (.07) (.02)
---------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on
investments (2.67) 3.32 .87 3.83 1.67
---------------------------------------------------------------------------------------------------------------------------------
Total from Investment
Operations (2.69) 3.32 .80 3.76 1.65
---------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income -- -- -- -- --
---------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.32) (1.37) (1.12) (.29) --
---------------------------------------------------------------------------------------------------------------------------------
Total distributions (.32) (1.37) (1.12) (.29) --
---------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $13.74 $ 16.75 $ 14.80 $ 15.12 $ 11.65
---------------------------------------------------------------------------------------------------------------------------------
Total return (c) (16.1%) 23.0% 5.8% 32.3% 16.5%
---------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net
assets (b) 1.13%* 1.15% 1.20% 1.35% 1.85%*
---------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment loss to average
net assets (.27%)* 0.00% (.42%) (.49%) (.99%)*
---------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 65% 49% 42% 33% 20%*
---------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 305 $ 371 $ 281 $ 185 $ 53
</TABLE>

(a) Net investment loss per share was based upon the average shares outstanding
during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the ratio of expenses to average net assets for Liberty Acorn USA reflects
gross custodian fees. This ratio net of custodian fees paid indirectly
would have been 1.79% for the period ended December 31, 1996.

(c) Total return is not annualized for periods less than one year. Class A, B
and C shares are subject to sales loads, account fees and rule 12b-1 fees
that are not reflected in the total return.

*Annualized

____
20
<PAGE>

Notes

________________________________________________________________________________

____
21
<PAGE>

Notes

________________________________________________________________________________

____
22
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn USA (formerly Acorn USA)

--------------------------------------------------------------------------------

[LOGO OF LIBERTY FUNDS]

ALL-STAR.COLONIAL.CRABBE HUSON.NEWPORT.STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (C) 2000
One Financial Center, Boston, MA 02111-2621, 1-800-426-3750
www.libertyfunds.com

<PAGE>

LIBERTY ACORN TWENTY Prospectus, September 29, 2000

Class A, B and C Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

--------------------------------------------------------------------------------
TABLE OF CONTENTS

<TABLE>
<S> <C>
LIBERTY ACORN TWENTY...................................................... 2
--------------------
Investment Goal........................................................... 2
Principal Investment Strategies........................................... 2
Principal Investment Risks................................................ 2
Performance History....................................................... 4
Your Expenses............................................................. 5

YOUR ACCOUNT.............................................................. 6
------------
How to Buy Shares......................................................... 6
Sales Charges............................................................. 7
How to Exchange Shares.................................................... 11
How to Sell Shares........................................................ 11
Fund Policy on Trading of Fund Shares..................................... 12
Distribution and Service Fees............................................. 13
Other Information About Your Account...................................... 13

MANAGING THE FUND......................................................... 17
-----------------
Investment Advisor........................................................ 17
Portfolio Manager......................................................... 17

OTHER INVESTMENT STRATEGIES AND RISKS..................................... 18
-------------------------------------
The Information Edge...................................................... 18
Stock Strength Comes First................................................ 18
Derivative Strategies..................................................... 19
Temporary Defensive Strategies............................................ 19

FINANCIAL HIGHLIGHTS...................................................... 20
--------------------
</TABLE>

------------------
Not FDIC Insured
May Lose Value
No Bank Guarantee
------------------
<PAGE>

Liberty Acorn Twenty

INVESTMENT GOAL
--------------------------------------------------------------------------------
Liberty Acorn Twenty seeks long-term growth of capital.

Liberty Acorn Twenty typically looks for companies with:

Additional strategies that are not principal investment strategies and the risks
associated with them are described later in this prospectus under "Other
Investment Strategies and Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

____
2
<PAGE>

Liberty Acorn Twenty

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of its assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

____
3
<PAGE>

Liberty Acorn Twenty

UNDERSTANDING PERFORMANCE

Calendar year total returns show the Fund's Class Z share performance for each
completed calendar year. They include the effects of Class Z
expenses. Class A, Class B and Class C shares are subject to sales charges, 12b-
1 fees and different expenses that are not reflected in the bar chart. If these
amounts were reflected, returns would be less than those shown.

Average annual total returns are measures of the Fund's Class Z performance over
the past one-year and life of the Fund periods. They include the effects of
Class Z expenses. The table shows for each class the Class Z performance
restated to reflect the effect of sales charges of the class.

The Fund's return is compared to the S&P Mid Cap 400 Index. The S&P Mid Cap 400
is an unmanaged, market value-weighted index of 400 midcap U.S. companies.
Unlike the Fund, an index is not an investment, does not incur fees or expenses
and is not professionally managed. It is not possible to invest directly in an
index.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

Because Class A, Class B and Class C shares have not been offered for a full
calendar year, the information provided in the bar chart below shows changes in
the Fund's performance from year to year by illustrating the Fund's calendar
year total returns for its Class Z shares. Class Z shares are offered to certain
investors through a separate prospectus. The performance table following the bar
chart shows how the Fund's average annual returns for (1) the Class Z shares and
(2) the Class Z shares, restated to reflect the sales charges of the Class A,
Class B and Class C shares, respectively, compare with those of broad measures
of market performance for one year and life of the Fund. The chart and table are
intended to illustrate some of the risks of investing in the Fund by showing the
changes in the Fund's Class Z performance. All returns include the reinvestment
of dividends and distributions. Performance results include the effect of
expense reduction arrangements. If these arrangements were not in place, then
performance would have been lower. Any expense reduction arrangements may be
discontinued at any time. As with all mutual funds, past performance does not
predict the Fund's future performance.

Calendar Year Total Returns (Class Z)/(1)/

--------------------------------------------------------------------------------

[Bar Chart]

Year Return
---- ------
1999 29.30%

--------------------------------------------------------------------------------

For period shown in bar chart: Best quarter: 4th quarter 1999, +14.35%
Worst quarter: 3rd quarter 1999, -7.13%

(1) Class Z shares are not offered through this prospectus, but Class A, Class
B and Class C shares would have substantially similar annual returns
because the shares are invested in the same portfolio of securities and
these returns differ only to the extent that the classes do not have the
same expenses.

Average Annual Total Returns -- for periods ended December 31, 1999/(2)/

<TABLE>
<CAPTION>
Life of the
Inception Date 1 Year Fund

<S> <C> <C> <C>
Class A 9/29/00 21.87% 27.20%
--------------------------------------------------------------------------------
Class B 9/29/00 24.30% 30.69%
--------------------------------------------------------------------------------
Class C 9/29/00 28.30% 34.20%
--------------------------------------------------------------------------------
Class Z 11/23/98 29.30% 34.20%
--------------------------------------------------------------------------------
S&P Mid Cap 400 N/A 14.72% 24.49%
</TABLE>

(2) Class A, Class B, and Class C are new classes of shares. Their performance
information includes returns of the Fund's Class Z shares (the oldest
existing Fund class) for periods prior to the inception of the newer
classes of shares. Class Z returns are not restated to reflect any
differences in expenses (such as Rule 12b-1 fees) between shares. If
differences in expenses were reflected, the returns for prior to the
inception of the newer classes of shares would be lower. Class Z shares
were initially offered on November 28, 1998; Class A, Class B and Class C
shares were initially offered on September 29, 2000.
____
4
<PAGE>

Liberty Acorn Twenty

UNDERSTANDING EXPENSES

Sales Charges are paid directly by shareholders to Liberty Funds Distributor,
Inc., the Fund's distributor.

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, 12b-1 fees and administrative costs
including pricing and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. The table does not take into account any
expense reduction arrangements discusssed in the footnotes to the Annual Fund
Operating Expenses table. It uses the following hypothetical conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the
same

. assumes reinvestment of all dividends
and distributions

. assumes Class B shares convert to
Class A shares after eight years

Shareholder Fees/(3)/ (paid directly from your investment)
<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Maximum sales charge (load) on purchases (%)
(as a percentage of the offering price) 5.75 None None
-------------------------------------------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions (%) (as a percentage of the
lesser of purchase price or redemption price) 1.00/(4)/ 5.00 1.00
-------------------------------------------------------------------------------------------------
Redemption fee
(5) (5) (5)
</TABLE>

(3) A $10 annual fee is deducted from accounts of less than $1,000 and paid to
the transfer agent.

(4) This charge applies only to certain Class A shares
bought without an initial sales charge that are sold within 18 months of
purchase.

(5) There is a $7.50 charge for wiring sale proceeds to your bank.

Annual Fund Operating Expenses (deducted directly from fund assets)
<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Management fees/(6)/(%) .90 .90 .90
-------------------------------------------------------------------------------------------------
Distribution and service (12b-1) fees (%) .35 1.00 1.00
-------------------------------------------------------------------------------------------------
Other expenses (%) .57 .57 .57
-------------------------------------------------------------------------------------------------
Total annual fund operating expenses/(7)/ (%) 1.82 2.47 2.47
</TABLE>

(6) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

(7) The Fund's Advisor has voluntarily agreed to reimburse the Fund for any
ordinary operating expenses (exclusive of distribution and service fees,
interest, taxes and extraordinary expenses, if any) exceeding 1.70%, 2.35%
and 2.35% of the average annual net assets for Class A, Class B and Class C
shares, respectively. This arrangement may be modified or terminated by
either the Fund or its advisor on 30 days' notice. As a result, the actual
total annual fund operating expenses for Class A, B and C shares would be
1.70%, 2.35%, and 2.35% of respectively.

Liberty Acorn Twenty

Example Expenses (your actual costs may be higher or lower)

<TABLE>
<CAPTION>
Class 1 Year 3 Years 5 Years 10 Years
<S> <C> <C> <C> <C>
Class A: $ 749 $1,115 $1,504 $2,589
-----------------------------------------------------------------------------------------------------
Class B: did not sell your shares $ 250 $ 770 $1,316 $2,646

sold all your shares at
the end of the period $ 750 $1,070 $1,516 $2,646
-----------------------------------------------------------------------------------------------------
Class C: did not sell your shares $ 250 $ 770 $1,316 $2,806

sold all your shares at
the end of the period $ 350 $ 770 $1,316 $2,806
</TABLE>

____
5
<PAGE>

Your Account

INVESTMENT MINIMUMS

Initial Investment........................................ $1,000
Subsequent Investments.................................... $ 50
Automatic Investment Plan*................................ $ 50
Retirement Plans*......................................... $ 25

* The initial investment minimum of $1,000 is waived on this plan.

HOW TO BUY SHARES
--------------------------------------------------------------------------------

Outlined below are the various options for buying shares:

Method Instructions

Through your Your financial advisor can help you establish your
financial advisor account and buy Fund shares on your behalf. Your
financial advisor may charge you fees for executing the
purchase for you.
--------------------------------------------------------------------------------
By check For new accounts, send a completed application and
(new account) check made payable to the Fund to the transfer agent,
Liberty Funds Services, Inc., P.O. Box 1722, Boston, MA
02105-1722.
--------------------------------------------------------------------------------

By exchange You or your financial advisor may acquire shares by
exchanging shares you own in one fund for shares of the
same class of the Fund at no additional cost. There may
be an additional charge if exchanging from a money
market fund. To exchange by telephone, call 1-800-422-
3737.
--------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your bank
account to your Fund account. To wire funds to your
Fund account, call 1-800-422-3737 to obtain a control
number and the wiring instructions.
--------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically transferring
transfer money from your bank account to your Fund account by
calling 1-800-422-3737. Electronic funds transfers may
take up to two business days to settle and be
considered in "good form." You must set up this feature
prior to your telephone request. Be sure to complete
the appropriate section of the application.
--------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your Fund
account. You can select a pre-authorized amount to be
sent via electronic funds transfer. Be sure to complete
the appropriate section of the application for this
feature.
--------------------------------------------------------------------------------

____
6
<PAGE>

Your Account

CHOOSING A SHARE CLASS

The Fund offers three classes of shares in this prospectus -- Class A, B and C.
Each share class has its own sales charge and expense structure.
Determining which share class is best for you depends on the dollar amount you
are investing and the number of years for which you are willing to invest. If
your financial advisor firm does not participate in the Class B discount
program, purchases of $250,000 or more must be for Class A or Class C shares
only. Purchases of $1 million or more can be made only in Class A shares. Based
on your personal situation, your financial advisor can help you decide which
class of shares makes the most sense for you.

Class A Sales Charges

<TABLE>
<CAPTION>
% of offering
As a % of price
the public As a % retained by
offering of your financial
Amount of purchase price investment advisor firm
<S> <C> <C> <C>
Less than $50,000 5.75 6.10 5.00
-------------------------------------------------------------------------------------------------
$50,000 to less than $100,000 4.50 4.71 3.75
-------------------------------------------------------------------------------------------------
$100,000 to less than $250,000 3.50 3.63 2.75
-------------------------------------------------------------------------------------------------
$250,000 to less than $500,000 2.50 2.56 2.00
-------------------------------------------------------------------------------------------------
$500,000 to less than $1,000,000 2.00 2.04 1.75
-------------------------------------------------------------------------------------------------
$1,000,000 or more 0.00 0.00 0.00
-------------------------------------------------------------------------------------------------
</TABLE>

Class A shares bought without an initial sales charge in accounts aggregating $1
million to $25 million at the time of purchase are subject to a 1.00% CDSC if
the shares are sold within 18 months of the time of purchase. Subsequent Class A
share purchases that bring your account value above $1 million are subject to a
CDSC if redeemed within 18 months of the date of purchase. The 18-month period
begins on the first day of the month following each purchase. The CDSC does not
apply to retirement plans purchasing shares through a fee-based program.

For Class A share purchases of $1 million or more, financial advisors receive a
commission from the distributor as follows:

Purchases Over $1 Million

Amount purchased Commission %

First $3 million 1.00
-----------------------------------------------------------
$3 million to less than $5 million 0.80
-----------------------------------------------------------
$5 million to less than $25 million 0.50
-----------------------------------------------------------
$25 million or more 0.25
-----------------------------------------------------------

The commission to financial advisors for Class A share purchases of $25 million
or more is paid over 12 months but only to the extent the shares remain
outstanding.

----
7
<PAGE>

Your Account

UNDERSTANDING CONTINGENT DEFERRED SALES CHARGES (CDSC)

Reduced Sales Charges for Larger Investments There are two ways for you to pay
a lower sales charge when purchasing Class A shares. The first is through Rights
of Accumulation. If the combined value of the Fund accounts maintained by you,
your spouse or your minor children reaches a discount level (according to the
chart on the previous page), your next purchase will receive the lower sales
charge. The second is by signing a Statement of Intent within 90 days of your
purchase. By doing so, you would be able to pay the lower sales charge on all
purchases by agreeing to invest a total of at least $50,000 within 13 months. If
your Statement of Intent purchases are not completed within 13 months, you will
be charged the applicable sales charge on the amount you had invested to that
date. In addition, certain investors may purchase shares at a reduced sales
charge or net asset value, which is the value of a Fund share excluding any
sales charges. See the Statement of Additional Information for a description of
these situations.

Class B shares Your purchases of Class B shares are at Class B shares' net
asset value. Class B shares have no front-end sales charge, but they do carry a
CDSC that is imposed only on shares sold prior to the completion of the periods
shown in the charts below. The CDSC generally declines each year and eventually
disappears over time. The distributor pays the financial advisor firm an up-
front commission on sales of Class B shares as depicted in the charts below.

Purchases of less than $250,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 5.00
-------------------------------------------------------------------------
Through second year 4.00
-------------------------------------------------------------------------
Through third year 3.00
-------------------------------------------------------------------------
Through fourth year 3.00
-------------------------------------------------------------------------
Through fifth year 2.00
-------------------------------------------------------------------------
Through sixth year 1.00
-------------------------------------------------------------------------
Longer than six years None

Commission to financial advisors is 5.00%.

Automatic conversion to Class A shares is eight years after purchase.

____
8
<PAGE>

Your Account

Purchases of $250,000 to less than $500,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 3.00
-------------------------------------------------------------------------
Through second year 2.00
-------------------------------------------------------------------------
Through third year 1.00
-------------------------------------------------------------------------
Longer than three years 0.00

Commission to financial advisors is 2.50%.

Automatic conversion to Class A shares is four years after purchase.

Purchases of $500,000 to less than $1 million:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Commission to financial advisors is 1.75%.

Automatic conversion to Class A shares is three years after purchase.

____
9
<PAGE>

Your Account

Class C shares Similar to Class B shares, your purchases of Class C shares are
at Class C's net asset value. Although Class C shares have no front-end
sales charge, they carry a CDSC of 1.00% that is applied to shares sold within
the first year after they are purchased. After holding shares for one year, you
may sell them at any time without paying a CDSC. The distributor pays the
financial advisor firm an up-front commission of 1.00% on sales of Class C
shares.

Class C Sales Charges

Years after purchase % deducted when shares are sold

Through one year 1.00
--------------------------------------------------------------------------
Longer than one year 0.00

----
10
<PAGE>

Your Account

HOW TO EXCHANGE SHARES
-------------------------------------------------------------------------------
You may exchange your shares for shares of the same share class of another fund
distributed by Liberty Funds Distributor, Inc. at net asset value. If your
shares are subject to a CDSC, you will not be charged a CDSC upon the exchange.
However, when you sell the shares acquired through the exchange, the shares sold
may be subject to a CDSC, depending upon when you originally purchased the
shares you exchanged. For purposes of computing the CDSC, the length of time you
have owned your shares will be computed from the date of your original purchase
and the applicable CDSC will be the CDSC of the original fund. Unless your
account is part of a tax-deferred retirement plan, an exchange is a taxable
event. Therefore, you may realize a gain or a loss for tax purposes. The Fund
may terminate your exchange privilege if the advisor determines that your
exchange activity is likely to adversely impact its ability to manage the Fund.
To exchange by telephone, call 1-800-422-3737.

HOW TO SELL SHARES
-------------------------------------------------------------------------------
Your financial advisor can help you determine if and when you should sell your
shares. You may sell shares of the Fund on any regular business day that the New
York Stock Exchange (NYSE) is open.

____
11
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions

By systematic You may automatically sell a specified dollar amount or
withdrawal plan percentage on a monthly, quarterly or semi-annual
basis if your account balance is at least $5,000 and have
the proceeds sent to you. This feature is not available
if you hold your shares in certificate form. Be sure to
complete the appropriate section of the account
application for this feature.
--------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may
take up to two business days to be received by your bank.
You must set up this feature prior to your request. Be
sure to complete the appropriate section of the account
application for this feature.

FUND POLICY ON TRADING OF FUND SHARES
--------------------------------------------------------------------------------

____
12
<PAGE>

Your Account

DISTRIBUTION AND SERVICE FEES
--------------------------------------------------------------------------------

____
13
<PAGE>

Your Account

____
14
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities
held by the Fund, net of expense incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of
securities held for more than 12 months and net short-term
capital gains, which are gains on sales of securities held
for a 12-month period or less.

Distribution Options The Fund distributes dividends in June and
December and any capital gains (including short-term capital gains) at least
annually. You can choose one of the options listed in the table below for these
distributions when you open your account. To change your distribution option
call 1-800-345-6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
--------------------------------------------------------------------------------

Reinvest all distributions in shares of another fund
--------------------------------------------------------------------------------

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

____
15
<PAGE>

Your Account

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

____
16
<PAGE>

Managing the Fund

INVESTMENT ADVISOR
--------------------------------------------------------------------------------
Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset
Management, L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago,
Illinois 60606, is the Fund's investment advisor. Liberty WAM and its
predecessor have managed mutual funds, including the Fund, since 1992. In its
duties as investment advisor, Liberty WAM runs the Fund's day-to-day business,
including placing all orders for the purchase and sale of the Fund's portfolio
securities. As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.90% of the Fund's
average daily net assets. Liberty WAM also receives an administrative services
fee from the Fund at the annual rate of .05% of the Fund's average daily net
assets.

PORTFOLIO MANAGER
--------------------------------------------------------------------------------
Liberty WAM uses a team to manage the Fund. Team members share responsibility
for providing ideas, information, and knowledge in managing the Fund, and each
team member has one or more particular areas of expertise. The portfolio
manager is responsible for making daily investment decisions, and utilize the
management team's input and advice when making buy and sell determinations.

John H. Park
Lead portfolio manager

John Park is a vice president of the Liberty Acorn Trust, and has managed
Liberty Acorn Twenty since its inception in 1998. He has been a member of the
domestic investment team at Liberty WAM and WAM since 1993, and was a principal
of WAM from 1998 to September 29, 2000. Mr. Park is also manager of a mutual
fund underlying variable insurance products. He is a CPA and earned both his BA
and MBA degrees from the University of Chicago.

----
17
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

The Fund's principal investment strategies and risks are described under
"Liberty Acorn Twenty - Principal Investment Strategies" and "Liberty Acorn
Twenty - Principal Investment Risks." In seeking to meet its investment goal,
the Fund may also invest in other securities and use certain other investment
techniques. These securities and investment techniques offer opportunities and
carry various risks.

THE INFORMATION EDGE
--------------------------------------------------------------------------------

The Fund invests in entrepreneurially managed smaller, mid-sized and larger
companies that it believes are not as well known by financial analysts and whose
domination of a niche creates the opportunity for superior earnings-growth
potential. Liberty WAM may identify what it believes are important economic,
social or technological trends (for example, the growth of out-sourcing as a
business strategy, or the productivity gains from the increasing use of
technology) and try to identify companies it thinks will benefit from those
trends.

The realization of this A strong balance sheet Once Liberty WAM
growth potential would gives management uncovers an attractive
likely produce superior greater flexibility to company, it identifies
performance that is pursue strategic a price that it
sustainable over time. objectives and is believes would also
essential to maintaining make the stock a good
a competitive advantage. value.
</TABLE>
--------------------------------------------------------------------------------
STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------
Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty WAM
analysts talk to top management, vendors, suppliers and competitors, whenever
possible.

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

____
18
<PAGE>

Other Investments Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------
The Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money than the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STEATEGIES
--------------------------------------------------------------------------------

At times, Liberty WAM may determine that adverse market conditions make it
desirable to temporarily suspend the Fund's normal investment activities. During
such times, the Fund may, but is not required to, invest in cash or
high-quality, short-term debt securities, without limit. Taking a temporary
defensive position may prevent the Fund from achieving its investment goal.
____
19
<PAGE>

Financial Highlights

The financial highlights tables are intended to help you understand the Fund's
financial performance. Because Class A, Class B and Class C shares are new
classes of shares, information is shown for the Fund's Class Z shares since
inception. The Fund's fiscal year runs from January 1 to December 31. Class Z
shares are offered to certain investors through separate prospectuses. Certain
information reflects financial results for a single Fund share. The total
returns in the table represent the rate that you would have earned (or lost) on
an investment in the Fund (assuming reinvestment of all dividends and
distributions). The information with respect to the six month period ended June
30, 2000 is unaudited. The information with respect to the year ended December
31, 1999 and the period ended December 31, 1998 is audited. For periods up to
and including the year ended 1999, this information has been derived from the
Fund's financial statements which have been audited by Ernst & Young LLP,
independent auditors, whose report, along with the Fund's audited financial
statements, is included in the Fund's annual report. You can request a free
annual report by calling 1-800-426-3750.

Liberty Acorn Twenty

<TABLE>
<CAPTION>
Six months
For a share outstanding ended June 30, 2000 Inception 11/23/98
throughout each period (unaudited) Year Ended 12/31/99 Through 12/31/98
------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
Class Z Class Z Class Z
------------------------------------------------------------------------------------------------------------------------
Net asset value, beginning of period $ 13.70 $ 10.71 $ 10.00
Income from Investment Operations:
------------------------------------------------------------------------------------------------------------------------
Net investment income (loss) (a) (.04) (.08) --
------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain
on investments .50 3.21 .71
------------------------------------------------------------------------------------------------------------------------
Total from investment operations .46 3.13 .71
------------------------------------------------------------------------------------------------------------------------
Less Distributions:
Dividends from net investment income -- (.14) --
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.89) -- --
Total distribution (.89) (.14) --
------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $ 13.27 $ 13.70 $ 10.71
------------------------------------------------------------------------------------------------------------------------
Total return 3.4% 29.3% 7.1%
------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net
assets (b)(c) 1.37%* (b) (c) 1.37% 1.41%*
------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income (loss)
to average net assets (c) (.57%)* (c) (.62)% .22%*
------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 170% 101% 173%*
------------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 61 $ 68 $ 34
</TABLE>

(a) Net investment income (loss) per share was based upon the average shares
outstanding during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the expense ratio reflects total expenses prior to the reduction of
custodian fees for cash balances it maintains with the custodian
("custodian fees paid indirectly"). This ratio net of custodian fees paid
indirectly would have been 1.35% for the period ended December 31, 1998,
the year ended December 31, 1999 and the six months ended June 30, 2000.

(c) Liberty Acorn Twenty was reimbursed by Liberty WAM for certain net expenses
from November 23, 1998 through December 31, 1999. Without the
reimbursement, the ratio of expenses (prior to custodian fees paid
indirectly) to average net assets and the ratio of net investment income to
average net assets would have been 1.83% and (.21%), respectively, for the
period ended 12/31/98, 1.41% and (.66%), respectively, for the year
ended 12/31/99 and 1.40% and (.60%), respectively, for the six months ended
June 30, 2000.

(d) Total return is not annualized for periods less than one year. Class A, B
and C shares are subject to sales loads, account fees and rule 12b-1 fees
that are not reflected in the total return.

* Annualized

____
20
<PAGE>

Notes

______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

____
21
<PAGE>

Notes

____
22
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------
You can get more information about the Fund's investments in the Fund's
semi-annual and annual reports to shareholders. The annual report contains a
discussion of the market conditions and investment strategies that significantly
affected the Fund's performance over its last fiscal year.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn Twenty (formerly Acorn Twenty)

--------------------------------------------------------------------------------

[LETTERHEAD OF LIBERTY FUNDS]

ALL-STAR . COLONIAL . CRABBE HUSON . NEWPORT . STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (c)2000
One Finacial Center, Boston, MA 02111-2621, 1-800-426-3750
www.liberty funds.com

<PAGE>

-------------------------------------------------------------------------------

LIBERTY ACORN FOREIGN FORTY Prospectus, September 29, 2000
-------------------------------------------------------------------------------

Class A, B and C Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

--------------------------------------------------------------------------------
T A B L E O F C O N T E N T S
<TABLE>
<S> <C>
LIBERTY ACORN FOREIGN FORTY 2
---------------------------
Investment Goal...................................................... 2
Principal Investment Strategies...................................... 2
Principal Investment Risks........................................... 2
Performance History.................................................. 4
Your Expenses........................................................ 5

YOUR ACCOUNT 6
------------
How to Buy Shares.................................................... 6
Sales Charges........................................................ 7
How to Exchange Shares............................................... 11
How to Sell Shares................................................... 11
Fund Policy on Trading of Fund Shares................................ 12
Distribution and Service Fees........................................ 13
Other Information About Your Account................................. 13

MANAGING THE FUND 17
-----------------
Investment Advisor................................................... 17
Portfolio Managers................................................... 17

OTHER INVESTMENT STRATEGIES AND RISKS 19
-------------------------------------
The Information Edge................................................. 19
Stock Strength Comes First........................................... 19
Derivative Strategies................................................ 20
Temporary Defensive Strategies....................................... 20

FINANCIAL HIGHLIGHTS 21
--------------------
</TABLE>

Not FDIC May Lose Value
-----------------
Insured No Bank Guarantee
<PAGE>

Liberty Acorn Foreign Forty

INVESTMENT GOAL
-------------------------------------------------------------------------------
Liberty Acorn Foreign Forty seeks long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
-------------------------------------------------------------------------------

Liberty Acorn Foreign Forty invests primarily in the stocks of medium- to
larger-sized companies based in developed markets (for example, Japan, Canada
and United Kingdom) outside the U.S. The Fund invests in at least three
countries. The Fund is a non-diversified fund that takes advantage of its
advisor's research and stock-picking capabilities to invest in a limited number
of foreign companies (between 40-60) with market capitalizations of $5 billion
to $15 billion, offering the potential to provide above-average growth over
time.

Liberty Acorn Foreign Forty typically looks for companies with:
. A strong business franchise that offers growth potential.
. Products and services that give the company a competitive advantage.
. A stock price the Fund's advisor believes is reasonable relative to the
assets and earning power of the company.

Liberty Acorn Foreign Forty is an international fund and invests the majority of
its assets in the stocks of foreign companies based in developed markets outside
the U.S.

Additional strategies that are not principal investment strategies and the risks
associated with them are described later in this prospectus under "Other
Investment Strategies and Risks."

PRINCIPAL INVESTMENT RISKS
-------------------------------------------------------------------------------

The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) which
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

Equity risk is the risk that stock prices will fall over short or extended
periods of time. Although the stock market has historically outperformed other
asset classes over the long term, the equity

---
2
<PAGE>

Liberty Acorn Foreign Forty

market tends to move in cycles and individual stock prices may fluctuate
drastically from day-to-day and may underperform other asset classes over an
extended period of time. Individual companies may report poor results or be
negatively affected by industry and/or economic trends and developments. The
prices of securities issued by such companies may suffer a decline in response.
These price movements may result from factors affecting individual companies,
industries or the securities market as a whole.

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of its assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

---
3
<PAGE>

Liberty Acorn Foreign Forty

UNDERSTANDING PERFORMANCE

The Fund's return is compared to the SSB World ex-U.S. Cap Range $2-10 Billion
Index. The SSB World ex-U.S. Cap Range $2-10 Billion Index is Salomon Smith
Barney's two to ten billion U.S. dollar security market subset of its Broad
Market Index. It represents a midcap developed market index, excluding the U.S.
Unlike the Fund, an index is not an investment, does not incur fees or expenses
and is not professionally managed. It is not possible to invest directly in an
index.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

Because Class A, Class B and Class C shares have not been offered for a full
calendar year, the information provided in the bar chart below shows changes in
the Fund's performance from year to year by illustrating the Fund's calendar
year total returns for its Class Z shares. Class Z shares are offered to certain
investors through a separate prospectus. The performance table following the bar
chart shows how the Fund's average annual returns for (1) the Class Z shares and
(2) the Class Z shares, restated to reflect the sales charges of the Class A,
Class B and Class C shares, respectively, compare with those of broad measures
of market performance for one year and for the life of the Fund. The chart and
table are intended to illustrate some of the risks of investing in the Fund by
showing the changes in the Fund's Class Z performance. All returns include the
reinvestment of dividends and distributions. Performance results include the
effect of expense reduction arrangements. If these arrangements were not in
place, then performance would have been lower. Any expense reduction
arrangements may be discontinued at any time. As with all mutual funds, past
performance does not predict the Fund's future performance.

Calendar Year Total Returns (Class Z)/(1)/

-------------------------------------------------------------------------------

[Bar Chart]

Year Return
---- ------
1999 81.60%

-------------------------------------------------------------------------------

For period shown in bar chart:
Best quarter: 4th quarter 1999, +46.65%
Worst quarter: 3rd quarter 1999, +3.90%

Average Annual Total Returns -- for periods ended December 31, 1999/(2)(3)/

<TABLE>
<CAPTION>
Inception Date 1 Year Life of the Fund
<S> <C> <C> <C>
Class A 9/29/00 71.16% 77.11%
-------------------------------------------------------------------------------
Class B 9/29/00 76.60% 83.46%
-------------------------------------------------------------------------------
Class C 9/29/00 80.60% 86.84%
-------------------------------------------------------------------------------
Class Z 11/23/98 81.60% 86.84%
-------------------------------------------------------------------------------
SSB Cap Range $2-10 B N/A 23.52% 24.72%
</TABLE>

(2) The Fund's performance during 1999 was achieved in a period of unusual
market conditions that are unlikely to continue.

(3) Class A, Class B, and Class C are new classes of shares. Their performance
information includes returns of the Fund's Class Z shares (the oldest
existing Fund class) for periods prior to the inception of the newer
classes of shares. Class Z returns are not restated to reflect any
difference in expenses (such as Rule 12b-1 fees) between Class Z shares and
the newer classes of shares. If differences in expenses were reflected, the
returns for prior to the inception of the newer classes of shares would be
lower. Class Z shares were initially offered on November 28, 1998; Class A,
Class B and Class C shares were initially offered on September 29, 2000.

---
4
<PAGE>

Liberty Acorn Foreign Forty

UNDERSTANDING EXPENSES

Sales Charges are paid directly by shareholders to Liberty Funds Distributor,
Inc., the Fund's distributor.

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, 12b-1 fees and administrative costs
including pricing and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. The table does not take into account any
expense reduction arrangements discussed in the footnotes to the Annual Fund
Operating Expense table. It uses the following hypothetical conditions:
. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

. assumes Class B shares convert to Class A shares after eight years

YOUR EXPENSES
-------------------------------------------------------------------------------

Expenses are one of several factors to consider before you invest in a mutual
fund. The tables below describe the fees and expenses you may pay when you buy,
hold and sell shares of the Fund.

Shareholder Fees/(4)/ (paid directly from your investment)

<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Maximum sales charge (load) on purchases (%)
(as a percentage of the offering price) 5.75 None None
-------------------------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions (%) (as a percentage of the
lesser of purchase price or redemption price) 1.00/(5)/ 5.00 1.00
-------------------------------------------------------------------------------
Redemption fee (6) (6) (6)
</TABLE>

(4) A $10 annual fee is deducted from accounts of less than $1,000 and paid to
the transfer agent.

(5) This charge applies only to certain Class A shares bought without an initial
sales charge that are sold within 18 months of purchase.

(6) There is a $7.50 charge for wiring sale proceeds to your bank.

Annual Fund Operating Expenses (deducted directly from fund assets)

<TABLE>
<CAPTION>
Class A Class B Class C
<S> <C> <C> <C>
Management fees/(7)/ (%) .95 .95 .95
-------------------------------------------------------------------------------
Distribution and service (12b-1) fees (%) .35 1.00 1.00
-------------------------------------------------------------------------------
Other expenses (%) .73 .73 .73
-------------------------------------------------------------------------------
Total annual fund operating expenses/(8)/ (%) 2.03 2.68 2.68
---- ---- ----
</TABLE>

(7) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

(8) The Fund's advisor has voluntarily agreed to reimburse the Fund for any
ordinary operating expenses (exclusive of distribution and service fees,
interest, taxes and extraordinary expenses, if any) exceeding 1.80%, 2.45%
and 2.45% of the average annual net assets for Class A, Class B and Class C,
respectively. This arrangement may be modified or terminated by either the
Fund or its advisor on 30 days' notice. As a result, the actual total annual
Fund operating expenses for Class A, B and C shares would be
1.80%, 2.45%, 2.45% respectively.

Example Expenses (your actual costs may be higher or lower)

Class 1 Year 3 Years 5 Years 10 Years

Class A: $769 $1,175 $1,605 $2,798
-------------------------------------------------------------------------------
Class B: did not sell your shares $271 $ 832 $1,420 $2,856

sold all your shares at
the end of the period $771 $1,132 $1,620 $2,856
-------------------------------------------------------------------------------
Class C: did not sell your shares $271 $ 832 $1,420 $3,012

sold all your shares at
the end of the period $371 $ 832 $1,420 $3,012

---
5
<PAGE>

Your Account

INVESTMENT MINIMUMS

Initial Investment ............................................... $1,000
Subsequent Investments............................................ $ 50

Automatic Investment Plan*........................................ $ 50

Retirement Plans*................................................. $ 25

* The initial investment minimum of $1,000 is waived on this plan.

HOW TO BUY SHARES
-------------------------------------------------------------------------------

Outlined below are the various options for buying shares:

Method Instructions

Through your Your financial advisor can help you establish your
financial advisor account and buy Fund shares on your behalf. Your
financial advisor may charge you fees for executing
the purchase for you.
-------------------------------------------------------------------------------
By check For new accounts, send a completed application and
(new account) check made payable to the Fund to the transfer
agent, Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
-------------------------------------------------------------------------------

By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your
quarterly statement, or send a letter of
instruction including your Fund name and account
number with a check made payable to the Fund to
Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
-------------------------------------------------------------------------------

By exchange You or your financial advisor may acquire shares by
exchanging shares you own in one fund for shares of
the same class of the Fund at no additional cost.
There may be an additional charge if exchanging
from a money market fund. To exchange by telephone,
call 1-800-422-3737.
-------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your
bank account to your fund account. To wire funds to
your fund account, call 1-800-422-3737 to obtain a
control number and the wiring instructions.
-------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically
transfer transferring money from your bank account to your
Fund account by calling 1-800-422-3737. Electronic
funds transfers may take up to two business days to
settle and be considered in "good form." You must
set up this feature prior to your telephone
request. Be sure to complete the appropriate
section of the application.
-------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your fund
account. You can select a pre-authorized amount to
be sent via electronic funds transfer. Be sure to
complete the appropriate section of the application
for this feature.
-------------------------------------------------------------------------------

---
6
<PAGE>

Your Account

CHOOSING A SHARE CLASS

The Fund offers three classes of shares in this prospectus -- Class A, B and C.
Each share class has its own sales charge and expense structure. Determining
which share class is best for you depends on the dollar amount you are investing
and the number of years for which you are willing to invest. If your financial
advisor firm does not participate in the Class B discount program, purchases of
$250,000 or more must be for Class A or Class C shares only. Purchases of $1
million or more can be made only in Class A shares. Based on your personal
situation, your financial advisor can help you decide which class of shares
makes the most sense for you.

SALES CHARGES
-------------------------------------------------------------------------------

You may be subject to an initial sales charge when you purchase, or a contingent
deferred sales charge (CDSC) when you sell, shares of the Fund. These sales
charges are described below. In certain circumstances, these sales charges are
waived, as described below and in the Statement of Additional Information.

Class A shares Your purchases of Class A shares generally are at the public
offering price. This price includes a sales charge that is based on the amount
of your initial investment when you open your account. A portion of the sales
charge is the commission paid to the financial advisor firm on the sale of Class
A shares. The sales charge you pay on additional investments is based on
the total amount of your purchase and the current value of your account. The
amount of the sales charge differs depending on the amount you invest as shown
in the table below.

Class A Sales Charges

<TABLE>
<CAPTION>
% of offering
As a % of price
the public As a % retained by
offering of your financial
Amount of purchase price investment advisor firm
<S> <C> <C> <C>
Less than $50,000 5.75 6.10 5.00
-------------------------------------------------------------------------------
$50,000 to less than $100,000 4.50 4.71 3.75
-------------------------------------------------------------------------------
$100,000 to less than $250,000 3.50 3.63 2.75
-------------------------------------------------------------------------------
$250,000 to less than $500,000 2.50 2.56 2.00
-------------------------------------------------------------------------------
$500,000 to less than $1,000,000 2.00 2.04 1.75
-------------------------------------------------------------------------------
$1,000,000 or more 0.00 0.00 0.00
-------------------------------------------------------------------------------
</TABLE>

Class A shares bought without an initial sales charge in accounts aggregating $1
million to $25 million at the time of purchase are subject to a 1.00% CDSC if
the shares are sold within 18 months of the time of purchase. Subsequent Class A
share purchases that bring your account value above $1 million are subject to a
CDSC if redeemed within 18 months of the date of purchase. The 18-month period
begins on the first day of the month following each purchase. The CDSC does not
apply to retirement plans purchasing shares through a fee-based program.

For Class A share purchases of $1 million or more, financial advisors receive a
commission from the distributor as follows:

Purchases Over $1 Million

Amount purchased Commission %

First $3 million 1.00
-------------------------------------------------------------------------------
$3 million to less than $5 million 0.80
-------------------------------------------------------------------------------
$5 million to less than $25 million 0.50
-------------------------------------------------------------------------------
$25 million or more 0.25

The commission to financial advisors for Class A share purchases of $25 million
or more is paid over 12 months but only to the extent the shares remain
outstanding.

---
7
<PAGE>

Your Account

UNDERSTANDING CONTINGENT DEFERRED SALES CHARGES (CDSC)

Class B shares Your purchases of Class B shares are at Class B shares' net
asset value. Class B shares have no front-end sales charge, but they do carry a
CDSC that is imposed only on shares sold prior to the completion of the periods
shown in the charts below. The CDSC generally declines each year and eventually
disappears over time. The distributor pays the financial advisor firm an up-
front commission on sales of Class B shares as depicted in the charts below.

Purchases of less than $250,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Through first year 5.00
-------------------------------------------------------------------------------
Through second year 4.00
-------------------------------------------------------------------------------
Through third year 3.00
-------------------------------------------------------------------------------
Through fourth year 3.00
-------------------------------------------------------------------------------
Through fifth year 2.00
-------------------------------------------------------------------------------
Through sixth year 1.00
-------------------------------------------------------------------------------
Longer than six years None

Commission to financial advisors is 5.00%.

Automatic conversion to Class A shares is eight years after purchase.

---
8
<PAGE>

Your Account

Purchases of $250,000 to less than $500,000:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Commission to financial advisors is 2.50%.

Automatic conversion to Class A shares is four years after purchase.

Purchases of $500,000 to less than $1 million:

Class B Sales Charges

% deducted when
Holding period after purchase shares are sold

Commission to financial advisors is 1.75%.

Automatic conversion to Class A shares is three years after purchase.

---
9
<PAGE>

Your Account

Class C Sales Charges

Years after purchase % deducted when shares are sold

Through one year 1.00
-------------------------------------------------------------------------------
Longer than one year 0.00

---
10
<PAGE>

Your Account

HOW TO EXCHANGE SHARES
-------------------------------------------------------------------------------

HOW TO SELL SHARES
--------------------------------------------------------------------------------

Your financial advisor can help you determine if and when you should sell your
shares. You may sell shares of the Fund on any regular business day that the New
York Stock Exchange (NYSE) is open.

---
11
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions

Through your You may call your financial advisor to place your sell
financial advisor order. To receive the current trading day's price, your
financial advisor firm must receive your request prior to
the close of the NYSE, usually 4:00 p.m. Eastern time.
-------------------------------------------------------------------------------
By exchange You or your financial advisor may sell shares by
exchanging from the Fund into the same share class of
another Liberty fund at no additional cost. To exchange
by telephone, call 1-800-422-3737.
-------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by
telephone and request that a check be sent to your
address of record by calling 1-800-422-3737, unless you
have notified the Fund of an address change within the
previous 30 days. The dollar limit for telephone sales is
$100,000 in a 30-day period. You do not need to set up
this feature in advance of your call. Certain
restrictions apply to retirement accounts. For details,
call 1-800-345-6611.
-------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock
power form along with any certificates to be sold to the
address below. In your letter of instruction, note your
Fund's name, share class, account number, and the dollar
value or number of shares you wish to sell. All account
owners must sign the letter, and signatures must be
guaranteed by either a bank, a member firm of a national
stock exchange or another eligible guarantor institution.
Additional documentation is required for sales by
corporations, agents, fiduciaries, surviving joint owners
and individual retirement account owners. For details,
call 1-800-345-6611.

By systematic You may automatically sell a specified dollar amount or
withdrawal plan percentage on a monthly, quarterly or semi-annual basis
if your account balance is at least $5,000 and have the
proceeds sent to you. This feature is not available if
you hold your shares in certificate form. Be sure to
complete the appropriate section of the account
application for this feature.
-------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may
take up to two business days to be received by your bank.
You must set up this feature prior to your request. Be
sure to complete the appropriate section of the account
application for this feature.

FUND POLICY ON TRADING OF FUND SHARES
-------------------------------------------------------------------------------

---
12
<PAGE>

Your Account

DISTRIBUTION AND SERVICE FEES
-------------------------------------------------------------------------------

OTHER INFORMATION ABOUT YOUR ACCOUNT
-------------------------------------------------------------------------------

---
13
<PAGE>

Your Account

you add money to your account and bring the value above $1,000 prior to the fee
date, the fee will not be deducted.

---
14
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities
held by the Fund, net of expenses incurred by the
Fund.
-------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of
securities held for more than 12 months and net short-term
capital gains, which are gains on sales of securities held
for a 12-month period or less.

Distribution Options The Fund distributes dividends in June and December and any
capital gains (including short-term capital gains) at least annually. You can
choose one of the options listed in the table below for these distributions when
you open your account. To change your distribution option call
1-800-345-6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
-----------------------------------------------------------

Reinvest all distributions in shares of another fund
----------------------------------------------------

Receive dividends in cash (see options below) and reinvest capital gains
------------------------------------------------------------------------------

Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.
---
15
<PAGE>

Your Account

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

---
16
<PAGE>

Managing the Fund

INVESTMENT ADVISOR
-------------------------------------------------------------------------------

Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset Management,
L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago, Illinois
60606, is the Fund's investment advisor. Liberty WAM and its predecessor have
managed mutual funds, including the Fund, since 1992. In its duties as
investment advisor, Liberty WAM runs the Fund's day-to-day business, including
placing all orders for the purchase and sale of the Fund's portfolio securities.
As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.95% of the Fund's
average daily net assets. Liberty WAM also receives an administrative services
fee from the Fund at the annual rate of .05% of the Fund's average daily net
assets.

PORTFOLIO MANAGERS
-------------------------------------------------------------------------------

Marcel P. Houtzager

Co-portfolio manager

Marcel Houtzager is a vice president of Liberty Acorn Trust, and has managed
Liberty Acorn Foreign Forty since its inception in 1998. He has been a member
of the international analytical team at Liberty WAM and at WAM since 1992, and
was a principal of WAM from 1995 to September 29, 2000. Mr. Houtzager also
manages an international mutual fund underlying variable insurance products and
the foreign portfolio of an investment company whose shares are offered only to
non-U.S. investors. He is a CFA and a CPA, and earned his BA from Pomona College
and his MBA from the University of California at Berkley.

---
17
<PAGE>

Managing the Fund

Roger D. Edgley

Co-portfolio manager

Roger Edgley is a vice president of Liberty Acorn Trust and became co-portfolio
manager of Liberty Acorn Foreign Forty in December 1999. He has been director of
International Research at Liberty WAM and WAM, and was a principal of WAM from
January 1999 to September 29, 2000. Mr. Edgley has been a member of the
international analytical team at Liberty WAM and at WAM since 1994. Prior to
that, Mr. Edgley was a securities analyst in Hong Kong. He is a CFA and was
educated in the United Kingdom, completing his MSc degree from the London School
of Economics.

---
18
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

The Fund's principal investment strategies and risks are described under
"Liberty Acorn Foreign Forty - Principal Investment Strategies" and "Liberty
Acorn Foreign Forty - Principal Investment Risks." In seeking to meet its
investment goal, the Fund may also invest in other securities and use certain
other investment techniques. These securities and investment techniques offer
opportunities and carry various risks.

THE INFORMATION EDGE
-------------------------------------------------------------------------------

<TABLE>
Growth Potential Financial Strength Fundamental Value
-------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock
. innovative marketing . adequate working price relative to
. managerial skill capital growth potential
. market niche . conservative . valuable assets
. good earnings accounting practices
prospects . adequate profit
. strong demand for margin
product

STOCK STRENGTH COMES FIRST
-------------------------------------------------------------------------------

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).

---
19
<PAGE>

Other Investment Strategies and Risks

However, securities purchased on a long-term basis may be sold within 12 months
after purchase due to changes in the circumstances of a particular company or
industry, or changes in general market or economic conditions.

DERIVATIVE STRATEGIES
-------------------------------------------------------------------------------
The Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money than the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STRATEGIES
-------------------------------------------------------------------------------

---
20
<PAGE>

Financial Highlights

The financial highlights table is intended to help you understand the Fund's
financial performance. Because Class A, Class B and Class C shares are new
classes of shares, information is shown for the Fund's Class Z shares since
inception. The Fund's fiscal year runs from January 1 to December 31. Class Z
shares are offered to certain investors through separate prospectuses. Certain
information reflects financial results for a single Fund share. The total
returns in the table represent the rate that you would have earned (or lost) on
an investment in the Fund (assuming reinvestment of all dividends and
distributions). The information with respect to the six month period ended June
30, 2000 is unaudited. The information with respect to the year ended December
31, 1999 and the period ended December 31, 1998 is audited. For periods up to
and including the year ended 1999, this information has been derived from the
Fund's financial statements which have been audited by Ernst & Young LLP,
independent auditors, whose report, along with the Fund's audited financial
statements, is included in the Fund's annual report. You can request a free
annual report by calling 1-800-426-3750.

Liberty Acorn Foreign Forty

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------
Six months
ended June 30, 2000 Year Ended Inception 11/23/98
For a share outstanding throughout each period (unaudited) 12/31/99 Through 12/31/98
--------------------------------------------------------------------------------------------------------------------
Class Z Class Z Class Z
--------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
Net asset value, beginning of period $ 19.93 $ 11.00 $ 10.00
--------------------------------------------------------------------------------------------------------------------
Income from Investment Operations:

Net investment loss (a) -- (.02) (.01)
--------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain
on investments (.12) 8.98 1.01
--------------------------------------------------------------------------------------------------------------------
Total from investment operations (.12) 8.96 1.00
--------------------------------------------------------------------------------------------------------------------
Less Distributions:
Dividends from net investment income (.03) -- --
--------------------------------------------------------------------------------------------------------------------
Distributions from net realized and unrealized
gains reportable for federal income taxes (.11) (.03) --
--------------------------------------------------------------------------------------------------------------------
Total Distributions (.14) (.03) --
--------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $ 19.67 $ 19.93 $ 11.00
--------------------------------------------------------------------------------------------------------------------
Total return (d) (0.6%) 81.6% 10.0%
--------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net assets (b)(c) 1.37% 1.48% 1.73%*
--------------------------------------------------------------------------------------------------------------------
Ratio of net investment loss to average net
assets (c) (.03%) (.17%) (.78%)*
--------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 74% 60% 90%*
--------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 144 $ 107 $ 16
</TABLE>

(a) Net investment loss per share was based upon the average shares outstanding
during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the expense ratio reflects total expenses prior to the reduction of
custodian fees for cash balances it maintains with the custodian
("custodian fees paid indirectly"). This ratio net of custodian fees paid
indirectly would have been 1.45% for the period ended December 31, 1998,
and the year ended.

(c) Liberty Acorn Foreign Forty was reimbursed by Liberty WAM for certain net
expenses from November 23, 1998 through December 31, 1999. Without the
reimbursement, the ratio of expenses (prior to custodian fees paid
indirectly) to average net assets and the ratio of net investment income to
average net assets would have been 2.70% and (1.75%), respectively, for the
period ended 12/31/98 and 1.57% and (.26%), respectively, for the year
ended 12/31/99.

(d) Total return is not annualized for periods less than one year. Class A, B
and C shares are subject to sales loads, account fees and rule 12b-1 fees
that are not reflected in the total return.

*Annualized

---
21
<PAGE>

Notes

_______________________________________________________________________________

---
22
<PAGE>

Notes

_______________________________________________________________________________

---
23
<PAGE>

FOR MORE INFORMATION
-------------------------------------------------------------------------------

You may wish to read the Statement of Additional Information for more
information on the Fund and the securities in which it invests. The Statement
of Additional Information is incorporated into this prospectus by reference,
which means that it is considered to be part of this prospectus.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn Foreign Forty (formerly Acorn Foreign Forty)

[LOGO OF LIBERTY FUNDS]

ALLSTAR. COLONIAL. CRABBE HUSON. NEWPORT. STEIN RUE ADVISOR

One Financial Center, Boston, MA 02111-2621, 1-800-426-3750

www.libertyfunds.com
<PAGE>

------------------------------------------------------------------------------
LIBERTY ACORN FUND Prospectus, September 29, 2000
-------------------------------------------------------------------------------
Class Z Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Only eligible investors may purchase Class Z shares. See "Your Account -
Eligible Investors" for more information.

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

--------------------------------------------------------------------------------
T A B L E O F C O N T E N T S

<TABLE>
<S> <C>
LIBERTY ACORN FUND 2
------------------
Investment Goal........................................................... 2
Principal Investment Strategies........................................... 2
Principal Investment Risks................................................ 2

Performance History....................................................... 4
Your Expenses............................................................. 5

YOUR ACCOUNT 6
------------
How to Buy Shares......................................................... 6
Eligible Investors........................................................ 7
Price of Fund Shares...................................................... 8
How to Exchange Shares.................................................... 8
How to Sell Shares........................................................ 8
Fund Policy on Trading of Fund Shares..................................... 9
Other Information About Your Account...................................... 10

MANAGING THE FUND 13
-----------------
Investment Advisor........................................................ 13
Portfolio Managers........................................................ 13

OTHER INVESTMENT
STRATEGIES AND RISKS 15
--------------------
The Information Edge...................................................... 15
Stock Strength Comes First................................................ 15
Derivative Strategies..................................................... 16
Temporary Defensive Strategies............................................ 16

FINANCIAL HIGHLIGHTS 17
--------------------
</TABLE>

---------------------------
Not FDIC May Lose Value
-----------------
Insured No Bank Guarantee
---------------------------
____
1
<PAGE>

Liberty Acorn Fund

INVESTMENT GOAL
--------------------------------------------------------------------------------

Liberty Acorn Fund seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------

Liberty Acorn Fund invests primarily in the stocks of small- and medium-sized
companies. The Fund generally invests in the stocks of companies with
capitalizations of less than $2 billion.

The Fund believes that these smaller companies, which are not as well
known by financial analysts, may offer higher return potential than the stocks
of larger companies.

Liberty Acorn Fund typically looks for companies with:

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------

The principal risks of investing in the Fund are described below. There are
many circumstances (including additional risks that are not described here) that
could prevent the Fund from achieving its investment goal. You may lose money
by investing in the Fund.

____
2
<PAGE>

Acorn Fund

from factors affecting individual companies, industries or the securities market
as a whole.

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stocks of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times, the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of it assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.
____
3
<PAGE>

Acorn Fund

UNDERSTANDING PERFORMANCE

CALENDAR YEAR TOTAL RETURNS show the Fund's Class Z share performance for each
of the last ten complete calendar years. They include the effects of Fund
expenses.

AVERAGE ANNUAL TOTAL RETURNS are measures of the Fund's performance over the
past one-year, five-year and ten-year periods. They include the effects of Fund
expenses.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year, five years and ten years. The chart and table are
intended to illustrate some of the risks of investing in the Fund by showing the
changes in the Fund's performance. All returns include the reinvestment of
dividends and distributions. As with all mutual funds, past performance does
not predict the Fund's future performance.

Calendar Year Total Returns

--------------------------------------------------------------------------------
[BAR CHART]

Year Return
---- ------
1990 (17.52%)
1991 47.35%
1992 24.23%
1993 32.32%
1994 (7.45%)
1995 20.80%
1996 22.55%
1997 24.98%
1998 6.02%
1999 38.38%

--------------------------------------------------------------------------------

For period shown in bar chart:
Best quarter: 4th quarter 1999, +21.94%
Worst quarter: 3rd quarter 1990, -23.77%

Average Annual Total Returns -- for periods ended December 31, 1999

<TABLE>
<CAPTION>
1 Year 5 Years 10 Years
<S> <C> <C> <C>
Class Z 33.38% 21.21% 17.07%
-------------------------------------------------------------------------------
S&P 500 21.04% 28.56% 18.21%
-------------------------------------------------------------------------------
Russell 2000 21.26% 16.69% 13.34%
</TABLE>

____
4

<PAGE>

Acorn Fund

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

Shareholder Fees (paid directly from your investment)

<TABLE>
<S> <C>
Maximum sales charge (load) on purchases None
----------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions None
----------------------------------------------------------------
Redemption fee (%) (as a percentage of
amount redeemed) None
</TABLE>

Annual Fund Operating Expenses (deducted directly from Fund assets)

<TABLE>
<S> <C>
Management fees/(1)/ (%) .69
----------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
----------------------------------------------------------------
Other expenses (%) .16
----------------------------------------------------------------
Total annual fund operating expenses (%) .85
----------------------------------------------------------------
</TABLE>

(1) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

Example Expenses (your actual costs may be higher or lower)

<TABLE>
<CAPTION>
1 Year 3 Years 5 Years 10 Years
<S> <C> <C> <C>
$87 $271 $471 $1,049
</TABLE>

____
5
<PAGE>

Your Account

HOW TO BUY SHARES
--------------------------------------------------------------------------------

If you are an Eligible Investor (described below), your shares will be bought at
the next calculated price after the Fund receives your purchase request in "good
form." "Good form" means that your payment has been received and your
application is complete, including all necessary signatures. The Fund reserves
the right to refuse a purchase order for any reason, including if the Fund
believes that doing so would be in the best interest of the Fund and its
shareholders.

Outlined below are the various options for buying shares:

Method Instructions
--------------------------------------------------------------------------------
By check For new accounts, send a completed application and
(new account) check made payable to the Fund to the transfer agent,
Liberty Funds Services, Inc., P.O. Box 1722, Boston, MA
02105-1722.
--------------------------------------------------------------------------------
By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your quarterly
statement, or send a letter of instruction including
the Fund name and account number with a check made
payable to the Fund to Liberty Funds Services, Inc.,
P.O. Box 1722, Boston, MA 02105-1722.
--------------------------------------------------------------------------------

By exchange You may acquire shares by exchanging shares you own in
one fund for shares of the same class of shares of the
Fund at no additional cost. There may be an additional
charge if exchanging from a money market fund. To
exchange by telephone, call 1-800-422-3737.
--------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your bank
account to your Fund account. To wire funds to your Fund
account, call 1-800-422-3737 to obtain a control number
and the wiring instructions.
--------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically transferring
transfer (existing money from your bank account to your Fund account by
account) calling 1-800-422-3737. Electronic funds transfers may
take up to two business days to settle and be considered
in "good form." You must set up this feature prior to
your telephone request. Be sure to complete the
appropriate section of the application.
--------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your Fund
account. You can select a pre-authorized amount to be
sent via electronic funds transfer. Be sure to complete
the appropriate section of the application for this
feature.
--------------------------------------------------------------------------------

By dividend You may automatically invest dividends distributed by
diversification one fund into the same class of shares of the Fund at
no additional sales charge. To invest your dividends in
the Fund, call 1-800-345-6611.
--------------------------------------------------------------------------------
Through an Contact your financial professional. Financial
intermediary professionals may charge fees for their services.

____
6
<PAGE>

Your Account

ELIGIBLE INVESTORS

Only Eligible Investors may purchase Class Z shares of the Fund, directly or by
exchange. Eligible Investors are subject to different minimum investment
requirements. Eligible Investors and their applicable investment minimums are:

$1,000 minimum initial investment
---------------------------------

. any shareholder (or family member of such shareholder) who owned shares of
any of the Liberty Acorn Funds on September 29, 2000 (when all of the
Trust's then outstanding shares were re-designated Class Z shares) and who
has since then continued to own shares of any funds distributed by Liberty
Funds Distributor, Inc.;

. any trustee of Liberty Acorn Trust, any employee of Liberty WAM, or a
member of the family of the trustee or employee; and

. any person or entity listed in the account registration for any account
(such as joint owners, trustees, custodians, and designated beneficiaries)
that held shares of any of the funds of Liberty Acorn Trust on September
29, 2000 and that has continued to hold shares of any funds distributed by.
Liberty Funds Distributor, Inc.

$100,000 minimum initial investment
-----------------------------------

. any client of a broker-dealer or registered investment advisor that
recommends Fund shares and charges an asset-based fee;

. any insurance company, trust company or bank, which is purchasing shares
for its own account;

. any endowment, investment company or foundation; and

. any client of an investment advisory affiliate of the distributor if the
client meets certain criteria established by the distributor and its
affiliate.

No minimum initial investment
-----------------------------

. any person investing all or part of the proceeds of a distribution,
"roll over" or transfer of assets into a Liberty IRA from any deferred
compensation plan which was a shareholder of any of the Liberty Acorn funds
on September 29, 2000, in which the investor was a participant and through
which the investor invested in one or more of the Liberty Acorn funds
immediately prior to the distribution, transfer or roll over.

If you have any questions about your eligibility to purchase Class Z shares of
the Fund, please call 800-345-6611. If you hold Fund shares through a broker-
dealer or other financial institution, your eligibility to purchase Class Z
shares may differ depending on that institution's policies.

The Fund reserves the right to change the criteria for eligible investors and
these investment minimums. No minimum investment applies to accounts
participating in the automatic investment plan. The Fund also reserves the right
to refuse a purchase order for any reason, including if it believes that doing
so would be in the best interest of the Fund and its shareholders.
____
7
<PAGE>

Your Account

CHOOSING A SHARE CLASS

The Fund offers one class of shares in this prospectus -- Class Z.

The Fund also offers three additional classes of shares -- Class A, B and C
shares are available through a separate prospectus. Each share class has its
own sales charge and expense structure. Determining which share class is best
for you depends on the dollar amount you are investing and the number of years
for which you are willing to invest. Based on your personal situation, your
investment advisor can help you decide which class of shares makes the most
sense for you. In general, anyone who is eligible to purchase Class Z shares,
which do not incur Rule 12b-1 fees or sales charges, should do so in preference
over other classes.

PRICE OF FUND SHARES

Your purchases of Class Z shares generally are at net asset value, which is the
value of a Fund share without any sales charge. Class Z shares are not subject
to an initial sales charge when purchased, or a contingent deferred sales charge
when sold.

If you purchase Class Z shares of the Fund through certain broker-dealers, banks
or other intermediaries (intermediaries), they may charge a fee for their
services. They may also place limits on your ability to use services the Fund
offers. There are no sales charges or limitations if you purchase shares
directly from the Fund, except as described in this prospectus.

If an intermediary is an agent or designee of the Fund, orders are processed at
the net asset value next calculated after the intermediary receives the order.
The intermediary must segregate any orders it receives after the close of
regular trading on the NYSE and transmit those orders separately for execution
at the net asset value next determined.

HOW TO EXCHANGE SHARES

You may exchange your shares for shares of the same share class of another fund
or Class A shares of certain other funds distributed by Liberty Funds
Distributor, Inc., at net asset value without a sales charge. Unless your
account is part of a tax-deferred retirement plan, an exchange is a taxable
event. Therefore, you may realize a gain or a loss for tax purposes. The Fund
may terminate your exchange privilege if the advisor determines that your
exchange activity is likely to adversely impact its ability to manage the Fund.
To exchange by telephone, call 1-800-422-3737.

HOW TO SELL SHARES

You may sell shares of the Fund on any regular business day that the New York
Stock Exchange (NYSE) is open.

When the Fund receives your sales request in "good form," shares will be sold at
the next calculated net asset value. In "good form" means that money used to
purchase your shares is fully collected. When selling shares by letter of
instruction, "good form" also means (i) your letter has complete instructions,
the proper signatures and signature guarantees, and (ii) any other required
documents are attached. A signature guarantee is designed to protect you and
Liberty Acorn from fraud. Signature guarantees can be obtained from a commercial
bank, broker-dealer, credit union (if authorized under state law), securities
exchange or association. A notary public cannot provide a signature guarantee.
For additional documents required for sales by corporations, agents, fiduciaries
and surviving joint owners, please call 1-800-345-6611. Retirement plan accounts
have special requirements; please call 1-800-799-7526 for more information.

____
8
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions

--------------------------------------------------------------------------------
By exchange You may sell shares by exchanging from the Fund into Class Z
shares or Class A shares of another fund at no additional
cost. To exchange by telephone, call 1-800-422-3737.
--------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by telephone
and request that a check be sent to your address of record
by calling 1-800-422-3737, unless you have notified the Fund
of an address change within the previous 30 days. The dollar
limit for telephone sales is $100,000 in a 30-day period.
You do not need to set up this feature in advance of your
call. Certain restrictions apply to retirement accounts. For
details, call 1-800-345-6611.
--------------------------------------------------------------------------------

By mail You may send a signed letter of instruction or stock power
form to the address below. In your letter of instruction,
note the Fund's name, share class, account number, and the
dollar value or number of shares you wish to sell. All
account owners must sign the letter, and signatures must be
guaranteed by either a bank, a member firm of a national
stock exchange or another eligible guarantor institution.
Additional documentation is required for sales by
corporations, agents, fiduciaries, surviving joint owners
and individual retirement account owners. For details, call
1-800-345-6611.

Mail your letter of instruction to Liberty Funds Services,
Inc., P.O. Box 1722, Boston, MA 02105-1722.
--------------------------------------------------------------------------------
By wire You may sell shares and request that the proceeds be wired
to your bank. You must set up this feature prior to your
telephone request. Be sure to complete the appropriate
section of the account application for this feature.
--------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may take
up to two business days to be received by your bank. You
must set up this feature prior to your request. Be sure to
complete the appropriate section of the account application
for this feature.
--------------------------------------------------------------------------------
Systematic You may automatically sell a specified dollar amount or
Withdrawal Plan percentage on a monthly, quarterly or semiannual basis if
your account balance is at least $5,000 and have the
proceeds sent to you. This feature is not available if you
hold your shares in certificate form. Be sure to complete
the appropriate section of the account application for this
feature.
--------------------------------------------------------------------------------
Through an Contact your financial professional. Financial
Intermediary professionals may charge fees for their services.

FUND POLICY ON TRADING OF FUND SHARES
--------------------------------------------------------------------------------

____
9
<PAGE>

Your Account

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------

How the Fund's Share Price is Determined The price of a Fund's Class Z shares is
its net asset value. The net asset value is determined at the close of regular
trading on the NYSE, usually 4:00 p.m. Eastern time, on each business day that
the NYSE is open (typically Monday through Friday).

When you request a transaction, it will be processed at the net asset value next
determined after your request is received in "good form" by the Fund (or an
authorized broker-dealer, financial services company, or other agent, some of
whom may charge a fee for their services). In most cases, in order to receive
that day's price, the Fund must receive your order before that day's
transactions are processed. If you request a transaction through an agent, that
agent must receive your order by the close of trading on the NYSE to receive
that day's price.

The Fund determines its net asset value for its Class Z shares by dividing total
net assets attributable to Class Z shares by the number of outstanding Class Z
shares. In determining the net asset value, the Fund must determine the price
of each security in its portfolio at the close of each trading day. Because the
Fund may hold securities that are traded on foreign exchanges, the value of
these securities may change on days when shareholders will not be able to buy or
sell Fund shares. This will affect the Fund's net asset value on the day it is
next determined. Securities for which market quotations are available are valued
each day at the current market value. However, where market quotations are not
available, or when the advisor believes that subsequent events have made them
unreliable, the Fund may use other data to determine the fair value of the
securities.

Share Certificates Share certificates are not available for Class Z shares.

____
10
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities held by
the Fund, net of expenses incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of securities
held for more than 12 months and net short-term capital gains,
which are gains on sales of securities held for a 12-month period
or less.

Distribution Options. The Fund distributes dividends in June and
December and any capital gains (including short-term capital gains) at least
annually. You can choose one of the options listed in the table below for these
distributions when you open your account. To change your distribution option
call 1-800-345-6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
--------------------------------------------------------------------------------

Reinvest all distributions in shares of another fund
--------------------------------------------------------------------------------

Receive dividends in cash (see options below) and reinvest capital gains
--------------------------------------------------------------------------------

Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

____
11
<PAGE>

Your Account

____
12
<PAGE>

Managing the Fund

INVESTMENT ADVISOR
--------------------------------------------------------------------------------

Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset Management,
L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago, Illinois
60606, is the Fund's investment advisor. Liberty WAM and its predecessor have
managed mutual funds, including the Fund, since 1992. In its duties as
investment advisor, Liberty WAM runs the Fund's day-to-day business, including
placing all orders for the purchase and sale of the Fund's portfolio securities.
As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.69% of the Fund's
average daily net assets. Liberty WAM also receives an administrative fee from
the Fund at the annual rate of .05% of the Fund's average daily net assets.

PORTFOLIO MANAGERS
--------------------------------------------------------------------------------

Ralph Wanger

Lead portfolio manager

Ralph Wanger is chief strategist of the Liberty Acorn Fund and has been
portfolio manager of Liberty Acorn Fund since its inception in 1970. He has
been president and a member of Liberty Acorn Trust's Board of Trustees since
1970. Mr. Wanger has been president of Liberty WAM since September 29, 2000 and
was a principal of WAM before that date. He is a Chartered Financial Analyst
(CFA), and earned his BS and MS degrees in Industrial Management from the
Massachusetts Institute of Technology.

Charles P. McQuaid

Co-portfolio manager

Charles McQuaid is a senior vice president and member of Liberty Acorn Trust's
Board of Trustees. He has been director of Domestic Research at Liberty WAM and
WAM,

____
13
<PAGE>

Managing the Fund

and was a principal of WAM until September 29, 2000. Mr. McQuaid has been a
member of Liberty Acorn Fund's management team since 1978. He is a CFA, and
earned his BBA from the University of Massachusetts and his MBA from the
University of Chicago.

____
14
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

The Fund's principal investment strategies and risks are described under
"Liberty Acorn Fund - Principal Investment Strategies" and "Liberty Acorn Fund -
Principal Investment Risks." In seeking to meet its investment goal, the Fund
may also invest in other securities and use certain other investment techniques.
These securities and investment techniques offer opportunities and carry various
risks.

THE INFORMATION EDGE
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock price
. innovative marketing . adequate working relative to growth
. managerial skill capital potential
. market niche . conservative
. good earnings accounting practices
prospects . adequate profit margin . valuable assets
. strong demand
for product

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

____
15
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------

____
16
<PAGE>

Financial Highlights

The financial highlights tables are intended to help you understand the Fund's
financial performance. Information is shown for the Fund's last five fiscal
years and for the six months ended June 30, 2000. The Fund's fiscal year runs
from January 1 to December 31. Certain information reflects financial results
for a single Fund share. The total returns in the table represent the rate that
you would have earned (or lost) on an investment in the Fund (assuming
reinvestment of all dividends and distributions). The information with respect
to the six month period ended June 30, 2000 is unaudited. The information with
respect to the last five years is audited. For periods up to and including the
year ended 1999, this information has been derived from the Fund's financial
statements which have been audited by Ernst & Young LLP, independent auditors,
whose report, along with the Fund's audited financial statements, is included in
the Fund's annual report. You can request a free annual report by calling 1-800-
426-3750.

Liberty Acorn Fund

Six Months
Ended June 30,
For a share outstanding throughout 2000 Year Ended
each period (unaudited) 1999 1998 1997 1996 1995
------------------------------------------------------------------------------------------------------------
Class Z Class Z Class Z Class Z Class Z Class Z
------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C> <C>
Net asset value, beginning of period $18.53 $16.85 $16.99 $15.04 $13.60 $12.24
------------------------------------------------------------------------------------------------------------
Income from Investment Operations:

Net investment income .06 .09 .04 .15 .09 .11
------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on
investments, foreign currency and
futures (.32) 5.22 .91 3.57 2.93 2.42
------------------------------------------------------------------------------------------------------------
Total from investment
operations (.26) 5.31 .95 3.72 3.02 2.53
============================================================================================================
Less distributions:
Dividends from net investment income (.05) (.09) (.03) (.16) (.11) (.09)
------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (1.00) (3.54) (1.06) (1.61) (1.47) (1.08)
------------------------------------------------------------------------------------------------------------
Total distributions (1.05) (3.63) (1.09) (1.77) (1.58) (1.17)
============================================================================================================
Net asset value, end of period $17.22 $18.53 $16.85 $16.99 $15.04 $13.60
------------------------------------------------------------------------------------------------------------
Total return (a) (1.41)% 33.4% 6.0% 25.0% 22.6% 20.8%
============================================================================================================
Ratios/supplemental data:

Ratio of expenses to average net
assets .84%* .85% .84% .56% .57% .57%
------------------------------------------------------------------------------------------------------------
Ratio of net investment income to
average net assets .62%* .49% .30% .75% .53% .89%
------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 35%* 34% 24% 32% 33% 29%
------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $3,818 $3,921 $3,549 $3,681 $2,842 $2,399
</TABLE>

(a) Total return is not annualized for periods less than one year.

*Annualized.
____
17
<PAGE>

Notes

________________________________________________________________________________

____
18
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You may wish to read the Statement of Additional Information for more
information on the Fund and the securities in which it invests. The Statement
of Additional Information is incorporated into this prospectus by reference,
which means that it is considered to be part of this prospectus.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

You can review and copy information about the Fund by visiting the following
location, and you can obtain copies, upon payment of a duplicating fee, by
electronic request at the E-mail address [email protected] or by writing the:

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust: 811-01829

. Liberty Acorn Fund (formerly Acorn Fund)
--------------------------------------------------------------------------------

[LETTERHEAD OF LIBERTY FUNDS]

ALL-STAR.COLONIAL.CRABBE HUSON.NEWPORT.STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (c) 2000
One Financial Center, Boston, MA 02111-2621,1-800-426-3750
www.libertyfunds.com

<PAGE>

--------------------------------------------------------------------------------

LIBERTY ACORN TWENTY Prospectus, September 29, 2000
--------------------------------------------------------------------------------

Class Z Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Only eligible investors may purchase Class Z shares. See "Your Account -
Eligible Investors" for more information.

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

--------------------------------------------------------------------------------
T A B L E O F C O N T E N T S

<TABLE>
<S> <C>
LIBERTY ACORN TWENTY 2
--------------------
Investment Goal.......................................................... 2
Principal Investment Strategies.......................................... 2
Principal Investment Risks............................................... 2

Performance History...................................................... 4
Your Expenses............................................................ 5

YOUR ACCOUNT 6
------------
How to Buy Shares........................................................ 6
Eligible Investors....................................................... 7
Price of Fund Shares..................................................... 8
How to Exchange Shares................................................... 8
How to Sell Shares....................................................... 8
Fund Policy on Trading of Fund Shares.................................... 9
Other Information About Your Account..................................... 10

MANAGING THE FUND 13
-----------------
Investment Advisor....................................................... 13
Portfolio Manager........................................................ 13

OTHER INVESTMENT
STRATEGIES AND RISKS 14
--------------------
The Information Edge..................................................... 14
Stock Strength Comes First............................................... 14
Derivative Strategies.................................................... 15
Temporary Defensive Strategies........................................... 15

FINANCIAL HIGHLIGHTS 16
--------------------
</TABLE>

Not FDIC May Lose Value
-----------------
Insured No Bank Guarantee

<PAGE>

Liberty Acorn Twenty

INVESTMENT GOAL
--------------------------------------------------------------------------------

Liberty Acorn Twenty seeks long-term growth of capital.

Liberty Acorn Twenty typically looks for companies with:

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

-----
2
<PAGE>

Liberty Acorn Twenty

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

------
3
<PAGE>

Liberty Acorn Twenty

UNDERSTANDING PERFORMANCE

Calendar year total returns show the Fund's Class Z share performance for each
completed calendar year. They include the effects of Fund expenses.

Average annual total returns are measures of the Fund's performance over the
past one-year and life of the Fund. They include the effects of Fund expenses.

The Fund's return is compared to the S&P Mid Cap 400 Index. The S&P Mid Cap 400
is an unmanaged, market value-weighted index of 400 mid cap U.S. companies.
Unlike the Fund, an index is not an investment, does not incur fees or expenses
and is not professionally managed. It is not possible to invest directly in an
index.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year and life of the Fund. The chart and table are intended
to illustrate some of the risks of investing in the Fund by showing the changes
in the Fund's performance. All returns include the reinvestment of dividends and
distributions. Performance results include the effect of expense reduction
arrangements. If these arrangements were not in place, then performance would
have been lower. Any expense reduction arrangements may be discontinued at any
time. As with all mutual funds, past performance does not predict the Fund's
future performance.

Calendar Year Total Returns
--------------------------------------------------------------------------------

[BAR CHART]
Year Returns
---- -------
'99 29.30%

--------------------------------------------------------------------------------

For period shown in bar chart:
Best quarter: 4th quarter 1999, +14.35%
Worst quarter: 3rd quarter 1999, - 7.13%

Average Annual Total Returns -- for periods ended December 31, 1999

Inception Date 1 Year Life of the Fund

Class Z 11/23/98 29.30% 34.20%
--------------------------------------------------------------------------------
S&P Mid Cap 400 N/A 14.72% 24.49%

______
4
<PAGE>

Liberty Acorn Twenty

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

Shareholder Fees (paid directly from your investment)

Maximum sales charge (load) on purchases None
-----------------------------------------------------------------------
Maximum deferred sales charge (load) on redemptions None

Redemption fee (%) (as a percentage of amount redeemed) None

Annual Fund Operating Expenses (deducted directly from Fund assets)

Management fees/(1)/ (%) .90
-----------------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
-----------------------------------------------------------------------
Other expenses (%) .51
-----------------------------------------------------------------------
Total annual fund operating expenses(2) (%) 1.41
-----------------------------------------------------------------------

(1) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

(2) The Fund's advisor has voluntarily agreed to reimburse the Fund for any
ordinary operating expenses (exclusive of distribution and service fees,
interest, taxes and extraordinary expenses, if any) exceeding 1.35% of its
average annual net assets. This arrangement may be modified or terminated by
either the Fund or its advisor on 30 days' notice to the other. As a result,
the actual total annual Fund operating expenses for Class Z would be 1.35%.

Example Expenses (your actual costs may be higher or lower)

1 Year 3 Years 5 Years 10 Years

$144 $446 $ 771 $1,691

-----
5
<PAGE>

Your Account

HOW TO BUY SHARES
--------------------------------------------------------------------------------
If you are an Eligible Investor (described below), your shares will be bought at
the next calculated price after the Fund receives your purchase request in "good
form." "Good form" means that your payment has been received and your
application is complete, including all necessary signatures. The Fund reserves
the right to refuse a purchase order for any reason, including if the Fund
believes that doing so would be in the best interest of the Fund and its
shareholders.

Outlined below are the various options for buying shares:

<TABLE>
<CAPTION>
Method Instructions
-------------------------------------------------------------------------------------------------------
<S> <C>
By check For new accounts, send a completed application and check made payable
(new account) to the Fund to the transfer agent, Liberty Funds Services, Inc., P.O. Box
1722, Boston, MA 02105-1722.
-------------------------------------------------------------------------------------------------------
By check For existing accounts, fill out and return the additional investment stub
(existing account) included in your quarterly statement, or send a letter of instruction
including the Fund name and account number with a check made
payable to the Fund to Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
-------------------------------------------------------------------------------------------------------
By exchange You may acquire shares by exchanging shares you own in one fund for shares
of the same class of shares of the Fund at no additional cost. There may be
an additional charge if exchanging from a money market fund. To exchange by
telephone, call 1-800-422-3737.

-------------------------------------------------------------------------------------------------------

By wire You may purchase shares by wiring money from your bank account to your
Fund account. To wire funds to your Fund account, call 1-800-422-3737
to obtain a control number and the wiring instructions.
-------------------------------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically transferring money from your
transfer (existing bank account to your Fund account by calling 1-800-422-3737.
account) Electronic funds transfers may take up to two business days to settle and
be considered in "good form." You must set up this feature prior to your
telephone request. Be sure to complete the appropriate section of the
application.
-------------------------------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments automatically from your
investment plan bank account to your Fund account. You can select a pre-authorized
amount to be sent via electronic funds transfer. Be sure to complete the
appropriate section of the application for this feature.
-------------------------------------------------------------------------------------------------------
By dividend You may automatically invest dividends distributed by one
diversification fund into the same class of shares of the Fund at no additional sales
charge. To invest your dividends in the Fund, call 1-800-345-6611.
-------------------------------------------------------------------------------------------------------
Through an Contact your financial professional. Financial professionals may charge
intermediary fees for their services.
</TABLE>

<PAGE>

Your Account

ELIGIBLE INVESTORS

Only Eligible Investors may purchase Class Z shares of the Funds, directly or by
exchange. Eligible Investors are subject to different minimum investment
requirements. Eligible Investors and their applicable investment minimums are:

$1,000 minimum initial investment
---------------------------------

. any trustee of Liberty Acorn Trust, any employee of Liberty WAM, or a
member of the family of the trustee or employee; and

$100,000 minimum initial investment
-----------------------------------
. any client of a broker-dealer or registered investment advisor that
recommends Fund shares and charges an asset-based fee;

. any insurance company, trust company or bank, which is purchasing shares
for its own account;

. any endowment, investment company or foundation; and

. any client of an investment advisory affiliate of the distributor if the
client meets certain criteria established by the distributor and its
affiliate.

No minimum initial investment
-----------------------------

Your Account

CHOOSING A SHARE CLASS

The Fund offers one class of shares in this prospectus -- Class Z.

The Fund also offers three additional classes of shares -- Class A, B and C
shares are available through a separate prospectus. Each share class has its own
sales charge and expense structure. Determining which share class is best for
you depends on the dollar amount you are investing and the number of years for
which you are willing to invest. Based on your personal situation, your
investment advisor can help you decide which class of shares makes the most
sense for you. In general, anyone who is eligible to purchase Class Z shares,
which do not incur Rule 12b-1 fees or sales charges, should do so in preference
over other classes.

PRICE OF FUND SHARES
--------------------------------------------------------------------------------

HOW TO EXCHANGE SHARES
--------------------------------------------------------------------------------

HOW TO SELL SHARES
--------------------------------------------------------------------------------
You may sell shares of the Fund on any regular business day that the New York
Stock Exchange (NYSE) is open.

----
8
<PAGE>

Your Account

Outlined below are the various options for selling shares:

<TABLE>

Method Instructions
---------------------------------------------------------------------------------------------------
<S> <C>
By exchange You may sell shares by exchanging from the Fund into Class Z shares or
Class A shares of another fund at no additional cost. To exchange by
telephone, call 1-800-422-3737.
---------------------------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by telephone and request
that a check be sent to your address of record by calling 1-800-422-3737,
unless you have notified the Fund of an address change within the
previous 30 days. The dollar limit for telephone sales is $100,000 in a
30-day period. You do not need to set up this feature in advance of your
call. Certain restrictions apply to retirement accounts. For details,
call 1-800-345-6611.
---------------------------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock power form to the
address below. In your letter of instruction, note the Fund's name, share
class, account number, and the dollar value or number of shares you
wish to sell. All account owners must sign the letter, and signatures must
be guaranteed by either a bank, a member firm of a national stock
exchange or another eligible guarantor institution. Additional
documentation is required for sales by corporations, agents, fiduciaries,
surviving joint owners and individual retirement account owners. For
details, call 1-800-345-6611.

Mail your letter of instruction to Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
---------------------------------------------------------------------------------------------------
By wire You may sell shares and request that the proceeds be wired to your
bank. You must set up this feature prior to your telephone request. Be
sure to complete the appropriate section of the account application for
this feature.
---------------------------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be electronically
funds transfer transferred to your bank. Proceeds may take up to two business days
to be received by your bank. You must set up this feature prior to your
request. Be sure to complete the appropriate section of the account
application for this feature.
---------------------------------------------------------------------------------------------------
Systematic You may automatically sell a specified dollar amount or percentage on a
Withdrawal Plan monthly, quarterly or semiannual basis if your account balance is at
least $5,000 and have the proceeds sent to you. This feature is not available
if you hold your shares in certificate form. Be sure to complete the appropriate
section of the account application for this feature.
---------------------------------------------------------------------------------------------------
Through an Contact your financial professional. Financial professionals may charge
Intermediary fees for their services.
</TABLE>

----
9
<PAGE>

Your Account

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------
How the Fund's Share Price is Determined The price of a Fund's Class Z shares is
its net asset value. The net asset value is determined at the close of regular
trading on the NYSE, usually 4:00 p.m. Eastern time, on each business day that
the NYSE is open (typically Monday through Friday).

Share Certificates Share certificates are not available for Class Z shares.

-----
10
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Capital gains Represents net long-term capital gains on sales of securities
held for more than 12 months and net short-term capital gains,
which are gains on sales of securities held for a 12-month period
or less.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
-------------------------------------------------------------------------------

Reinvest all distributions in shares of another fund
-------------------------------------------------------------------------------
Receive dividends in cash (see options below) and reinvest capital gains
-------------------------------------------------------------------------------
Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on federal, state, local or other applicable tax
laws.

____
11
<PAGE>

Your Account

____
12
<PAGE>

Managing the Fund

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.90% of the Fund's
average daily net assets. Liberty WAM also receives an administrative fee from
the Fund at the annual rate of .05% of the Fund's average daily net assets.

PORTFOLIO MANAGER
--------------------------------------------------------------------------------
Liberty WAM uses a team to manage the Fund. Team members share responsibility
for providing ideas, information, and knowledge in managing the Fund, and each
team member has one or more particular areas of expertise. The portfolio manager
is responsible for making daily investment decisions, and utilizes the
management team's input and advice when making buy and sell determinations.

John H. Park

Lead portfolio manager

____
13
<PAGE>

OTHER INVESTMENT STRATEGIES AND RISKS

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

THE INFORMATION EDGE
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock price
. innovative marketing . adequate working relative to growth
. managerial skills capital potential
. market niche . conservative . valuable assets
. good earnings accounting practices
prospects . adequate profit margin
. strong demand
for product

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------
Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty WAM
analysts talk to top management, vendors, suppliers and competitors, whenever
possible.

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

____
14
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------
The Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money than the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------
At times, Liberty WAM may determine that adverse market conditions make it
desirable to temporarily suspend the Fund's normal investment activities. During
such times, the Fund may, but is not required to, invest in cash or high-
quality, short-term debt securities, without limit. Taking a temporary defensive
position may prevent the Fund from achieving its investment goal.
____
15
<PAGE>

Financial Highlights

The financial highlights table is intended to help you understand the Fund's
financial performance. Information is shown for the Fund's Class Z shares since
inception. The Fund's fiscal year runs from January 1 to December 31. Certain
information reflects financial results for a single Fund share. The total
returns in the table represent the rate that you would have earned (or lost) on
an investment in the Fund (assuming reinvestment of all dividends and
distributions). The information with respect to the six-month period ended June
30, 2000 is unaudited. The information with respect to the year ended December
31, 1999 and the period ended December 31, 1998 is audited. For periods up to
and including the year ended 1999, this information has been derived from the
Fund's financial statements which have been audited by Ernst & Young LLP,
independent auditors, whose report, along with the Fund's audited financial
statements, is included in the Fund's annual report. You can request a free
annual report by calling 1-800-426-3750.

Liberty Acorn Twenty

<TABLE>
<CAPTION>
Six months
ended
6/30/00 Inception 11/23/98
For a share outstanding throughout each period (unaudited) Year ended 12/31/99 Through 12/31/98
-------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
Class Z Class Z Class Z
-------------------------------------------------------------------------------------------------------------------
Net asset value, beginning of period $13.70 $10.71 $ 10.00
-------------------------------------------------------------------------------------------------------------------
Income from investment Operations:

Net investment income (loss) (a) (.04) (.08) --
-------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on investments .50 3.21 .71
-------------------------------------------------------------------------------------------------------------------
Total from investment operations .46 3.13 .71
-------------------------------------------------------------------------------------------------------------------
Less Distributions:
Dividends from net investment income -- -- --
Distribution from net realized and unrealized gains
reportable for federal income taxes (.89) (.14) --
-------------------------------------------------------------------------------------------------------------------
Total distributions (.89) (.14) --
-------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $13.27 $13.70 $ 10.71
-------------------------------------------------------------------------------------------------------------------
Total return (d) 3.4% 29.3% 7.1%
-------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:
-------------------------------------------------------------------------------------------------------------------
Ratio of expenses to average net assets (b)(c) 1.37%* 1.37% 1.41%*
-------------------------------------------------------------------------------------------------------------------
Ratio of net investment income (loss)
to average net assets (c) (.57%)* (.62)% .22%*
-------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 170%* 101% 173%*
-------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 61 $ 68 $ 34
</TABLE>

<TABLE>
<S> <C>
(a) Net investment income (loss) per (c) Liberty Acorn Twenty was reimbursed
share was based upon the average by Liberty WAM for certain net
shares outstanding during the period. expenses from November 23, 1998
through June 30, 2000. Without
(b) In accordance with a requirement by the reimbursement, the ratio of
the Securities and Exchange expenses (prior to custodian fees paid
Commission, the expense ratio indirectly) to average net assets and
reflects total expenses prior to the the ratio of net investment income to
reduction of custodian fees for cash average net assets would have been
balances it maintains with the 1.83% and (.21%), respectively, for
custodian ("custodian fees paid the period ended 12/31/98, 1.41%
indirectly"). This ratio net of custodian and (.66%), respectively, for the year
fees paid indirectly would have been ended 12/31/99 and 1.40% and (.60%),
1.35% for the period ended December 31, respectively, for the six months
1998, the year ended December 31, 1999 ended June 30, 2000.
and the six months ended June 30, 2000.
(d) Total return is not annualized for
periods less than one year.

* Annualized
</TABLE>

____
16
<PAGE>

Notes

---
17

<PAGE>

Notes
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---
18
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You can get more information about the Fund's investments in the Fund's semi-
annual and annual reports to shareholders. The annual report contains a
discussion of the market conditions and investment strategies that significantly
affected the Fund's performance over its last fiscal year.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn Twenty (formerly Acorn Twenty)

--------------------------------------------------------------------------------

[LOGO OF LIBERTY FUNDS]

ALL-STAR.COLONIAL.CRABBE HUSON.NEWPORT.STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (c) 2000
One Financial Center, Boston, MA 02111-2621, 1-800-426-3750
www.libertyfunds.com

<PAGE>

--------------------------------------------------------------------------------

LIBERTY ACORN INTERNATIONAL Prospectus, September 29, 2000
--------------------------------------------------------------------------------

Class Z Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Only eligible investors may purchase Class Z shares. See "Your Account -
Eligible Investors" for more information.

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

--------------------------------------------------------------------------------
T A B L E OF C O N T E N T S

<TABLE>
<S> <C>
LIBERTY ACORN INTERNATIONAL 2
---------------------------
Investment Goal......................................................... 2
Principal Investment Strategies......................................... 2
Principal Investment Risks.............................................. 2
Performance History..................................................... 4
Your Expenses........................................................... 5

YOUR ACCOUNT 6
------------
How to Buy Shares....................................................... 6
Eligible Investors...................................................... 7
Price of Fund Shares.................................................... 8
How to Exchange Shares.................................................. 8
How to Sell Shares...................................................... 8
Fund Policy on Trading of Fund Shares................................... 9
Other Information About Your Account.................................... 10

MANAGING THE FUND 13
-----------------
Investment Advisor...................................................... 13
Portfolio Managers...................................................... 13

OTHER INVESTMENT
STRATEGIES AND RISKS 15
--------------------

The Information Edge.................................................... 15
Stock Strength Comes First.............................................. 15
Derivative Strategies................................................... 16
Temporary Defensive Strategies.......................................... 16

FINANCIAL HIGHLIGHTS 17
--------------------
</TABLE>

Not FDIC May Lose Value
-----------------
Insured No Bank Guarantee

____
1
<PAGE>

Liberty Acorn International

INVESTMENT GOAL
--------------------------------------------------------------------------------

Liberty Acorn International seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
--------------------------------------------------------------------------------

The Fund believes that smaller companies - particularly outside the U.S. -that
are not as well known by financial analysts may offer higher return potential
than the stocks of larger companies.

Liberty Acorn International typically looks for companies with:

. A strong business franchise that offers growth potential.

. Products and services that give the company a competitive advantage.

. A stock price the Fund's advisor believes is reasonable relative to the
assets and earning power of the company.

Liberty Acorn International is an international fund and invests the majority
(under normal market conditions, at least 75%) of its total assets in the stocks
of foreign companies based in developed markets (for example, Japan, Canada and
United Kingdom) and emerging markets (for example, Mexico, Brazil and Korea).

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
--------------------------------------------------------------------------------

Liberty Acorn International

from factors affecting individual companies, industries or the securities market
as a whole.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

____
3
<PAGE>

Liberty Acorn International

UNDERSTANDING PERFORMANCE

Calendar year total returns show the Fund's Class Z share performance for each
completed calendar year. They include the effects of Fund expenses.

Average annual total returns are measures of the Fund's performance over the
past one-year, five-year and life of the Fund periods. They include the effects
of Fund expenses.

The Fund's return is compared to Morgan Stanley's Europe, Australasia and Far
East Index (EAFE), an index of companies throughout the world in proportion to
stock market capitalizations, excluding the U.S. and Canada, and the EMI (world
ex-U.S.), Salomon Smith Barney's index of the bottom 20% of institutionally
investable capital of countries, selected by Salomon and excluding the U.S.
Unlike the Fund, indices are not investments, do not incur fees or expenses and
are not professionally managed. It is not possible to invest directly in
indices.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year, five years and life of the Fund. The chart and table
are intended to illustrate some of the risks of investing in the Fund by showing
the changes in the Fund's performance. All returns include the reinvestment of
dividends and distributions. As with all mutual funds, past performance does not
predict the Fund's future performance.

Calendar Year Total Returns/(1)/

--------------------------------------------------------------------------------
[BAR CHART]

Year Return
---- ------
1993 49.11%
1994 (3.80%)
1995 8.93%
1996 20.65%
1997 19.00%
1998 15.43%
1999 79.19%

--------------------------------------------------------------------------------

For period shown in bar chart: Best quarter: 4th quarter 1999, +41.63%
Worst quarter: 3rd quarter 1998, -16.05%

Average Annual Total Returns -- For Periods Ended December 31, 1999/(1)/

Inception Life Of The
Date 1 Year 5 Years Fund

Class Z 9/23/92 79.19% 22.19% 21.71%
--------------------------------------------------------------------------------
EAFE N/A 26.96% 12.83% 13.50%
--------------------------------------------------------------------------------
EMI (world ex-U.S.) N/A 23.52% 7.21% 9.48%

(1) The Fund's performance in 1999 was achieved during a period of unusual
market conditions that are unlikely to continue.

____
4
<PAGE>

Liberty Acorn International

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

YOUR EXPENSES
--------------------------------------------------------------------------------

Expenses are one of several factors to consider before you invest in a mutual
fund. The tables below describe the fees and expenses you may pay when you buy,
hold and sell shares of the Fund.

Shareholder Fees (paid directly from your investment)

Maximum sales charge (load) on purchases None
------------------------------------------------------------------

Maximum deferred sales charge (load) on
redemptions None
------------------------------------------------------------------

Redemption fee (%) (as a percentage of
amount redeemed) None

Annual Fund Operating Expenses (deducted directly from Fund assets)

Management fees /(2)/(%) .81
------------------------------------------------------------------

Distribution and service (12b-1) fees (%) None
------------------------------------------------------------------

Other expenses (%) .30
------------------------------------------------------------------

Total annual fund operating expenses (%) 1.11
------------------------------------------------------------------

(2) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

Example Expenses (your actual costs may be higher or lower)

1 Year 3 Years 5 Years 10 Years

$113 $353 $612 $1,352
____
5
<PAGE>

Your Account

HOW TO BUY SHARES
--------------------------------------------------------------------------------

Outlined below are the various options for buying shares:

Method Instructions

--------------------------------------------------------------------------------
By check For new accounts, send a completed application and check
(new account) made payable to the Fund to the transfer agent, Liberty
Funds Services, Inc., P.O. Box 1722, Boston, MA 02105-
1722.
--------------------------------------------------------------------------------
By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your quarterly
statement, or send a letter of instruction including the
Fund name and account number with a check made payable
to the Fund to Liberty Funds Services, Inc., P.O. Box
1722, Boston, MA 02105-1722.
--------------------------------------------------------------------------------

____
6
<PAGE>

Your Account

ELIGIBLE INVESTORS
--------------------------------------------------------------------------------

$1,000 minimum initial investment
---------------------------------

. any trustee of Liberty Acorn Trust, any employee of Liberty WAM, or a
member of the family of the trustee or employee; and

. any person or entity listed in the account registration for any account
(such as joint owners, trustees, custodians, and designated beneficiaries)
that held shares of any of the funds of Liberty Acorn Trust on September
29, 2000 and that has continued to hold shares of any funds distributed by
Liberty Funds Distributor, Inc.

$100,000 minimum initial investment
-----------------------------------

. any client of a broker-dealer or registered investment advisor that
recommends Fund shares and charges an asset-based fee;

. any insurance company, trust company or bank, which is purchasing shares
for its own account;

. any endowment, investment company or foundation; and

. any client of an investment advisory affiliate of the distributor if the
client meets certain criteria established by the distributor and its
affiliate.

No minimum initial investment
-----------------------------

If you have any questions about your eligibility to purchase Class Z shares of
the Fund, please call 1-800-345-6611. If you hold Fund shares through a broker-
dealer or other financial institution, your eligibility to purchase Class Z
shares may differ depending on that institution's policies.

Your Account

CHOOSING A SHARE CLASS

The Fund offers one class of shares in this prospectus -- Class Z.

PRICE OF FUND SHARES
--------------------------------------------------------------------------------

HOW TO EXCHANGE SHARES
--------------------------------------------------------------------------------

You may exchange your shares for shares of the same class of another fund or
Class A shares of certain other funds distributed by Liberty Funds Distributor,
Inc., at net asset value without a sales charge. Unless your account is part of
a tax-deferred retirement plan, an exchange is a taxable event. Therefore, you
may realize a gain or a loss for tax purposes. The Fund may terminate your
exchange privilege if the advisor determines that your exchange activity is
likely to adversely impact its ability to manage the Fund. To exchange by
telephone, call 1-800-422-3737.

HOW TO SELL SHARES
--------------------------------------------------------------------------------

You may sell shares of the Fund on any regular business day that the New York
Stock Exchange (NYSE) is open.

____
8
<PAGE>

Your Account
Outlined below are the various options for selling shares:

<TABLE>
<CAPTION>
Method Instructions

----------------------------------------------------------------------------------------------------
<S> <C>
By exchange You may sell shares by exchanging from the Fund into Class Z shares or
Class A shares of another fund at no additional cost. To exchange by
telephone, call 1-800-422-3737.
----------------------------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by telephone and request
that a check be sent to your address of record by calling 1-800-422-3737,
unless you have notified the Fund of an address change within the
previous 30 days. The dollar limit for telephone sales is $100,000 in a
30-day period. You do not need to set up this feature in advance of your
call. Certain restrictions apply to retirement accounts. For details,
call 1-800-345-6611.
----------------------------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock power form to the
address below. In your letter of instruction, note the Fund's name, share
class, account number, and the dollar value or number of shares you
wish to sell. All account owners must sign the letter, and signatures
must be guaranteed by either a bank, a member firm of a national stock
exchange or another eligible guarantor institution. Additional
documentation is required for sales by corporations, agents, fiduciaries,
surviving joint owners and individual retirement account owners. For
details, call 1-800-345-6611.

Mail your letter of instruction to Liberty Funds Services, Inc., P.O. Box
1722, Boston, MA 02105-1722.
----------------------------------------------------------------------------------------------------
By wire You may sell shares and request that the proceeds be wired to your
bank. You must set up this feature prior to your telephone request. Be
sure to complete the appropriate section of the account application for
this feature.
----------------------------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be electronically
funds transfer transferred to your bank. Proceeds may take up to two business days
to be received by your bank. You must set up this feature prior to your
request. Be sure to complete the appropriate section of the account
application for this feature.
----------------------------------------------------------------------------------------------------
Systematic You may automatically sell a specified dollar amount or percentage on a
Withdrawal Plan monthly, quarterly or semiannual basis if your account balance is at
least $5,000 and have the proceeds sent to you. This feature is not available
if you hold your shares in certificate form. Be sure to complete the
appropriate section of the account application for this feature.
----------------------------------------------------------------------------------------------------
Through an Contact your financial professional. Financial professionals may charge
Intermediary fees for their services.
----------------------------------------------------------------------------------------------------
</TABLE>

____
9
<PAGE>

Your Account

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------

How the Fund's Share Price is Determined The price of a Fund's Class Z shares
is its net asset value. The net asset value is determined at the close of
regular trading on the NYSE, usually 4:00 p.m. Eastern time, on each business
day that the NYSE is open (typically Monday through Friday).

The Fund determines its net asset value for its Class Z shares by dividing total
net assets attributable to Class Z shares by the number of outstanding Class Z
shares. In determining the net asset value, the Fund must determine the price of
each security in its portfolio at the close of each trading day. Because the
Fund may hold securities that are traded on foreign exchanges, the value of
these securities may change on days when shareholders will not be able to buy or
sell Fund shares. This will affect the Fund's net asset value on the day it is
next determined. Securities for which market quotations are available are valued
each day at the current market value. However, where market quotations are not
available, or when the advisor believes that subsequent events have made them
unreliable, the Fund may use other data to determine the fair value of the
securities.

Share Certificates Share certificates are not available for Class Z shares.

____
10
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities held
by the Fund net of expenses incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of securities
held for more than 12 months and net short-term capital gains,
which are gains on sales of securities held for a 12-month
period or less.

Distribution Options. The Fund distributes dividends in June and December and
any capital gains (including short-term capital gains) at least annually. You
can choose one of the options listed in the table below for these distributions
when you open your account. To change your distribution option call 1-800-345-
6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
--------------------------------------------------------------------------------

Reinvest all distributions in shares of another fund
--------------------------------------------------------------------------------
Receive dividends in cash (see options below) and reinvest capital gains
--------------------------------------------------------------------------------
Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

Tax Consequences Regardless of whether you receive your distributions in cash
or reinvest them in additional Fund shares, all Fund distributions are subject
to federal income tax. Depending on the state where you live, distributions may
also be subject to state and local income taxes.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

____
11
<PAGE>

Your Account

____
12
<PAGE>

Managing the Fund

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.81% of the Fund's
average daily net assets. Liberty WAM also receives an administrative fee from
the Fund at the annual rate of .05% of the Fund's average daily net assets.

Leah J. Zell

Lead portfolio manager

Margaret M. Forster

Co-portfolio manager

Margaret Forster is a vice president of Liberty Acorn Trust and became co-
portfolio manager of Liberty Acorn International in May 1999. She has been a
member of the

____
13
<PAGE>

Managing the Fund

international analytical team at Liberty WAM and WAM since 1994, and was a
principal of WAM from January 1999 to September 29, 2000. Prior to that, Ms.
Forster was a professor of finance at Northwestern and Ohio State Universities,
and an economist with the International Monetary Fund. She is a CFA. Her degrees
include a BS from Universidade de Sao Paulo, Escola Politecnica, Brazil, and an
MBA, MS and PhD from Cornell University.

____
14
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

THE INFORMATION EDGE
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
-------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock
. innovative marketing . adequate working price relative to
. managerial skill capital growth potential
. market niche . conservative . valuable assets
. good earnings prospects accounting practices
. strong demand for . adequate profit margin
product

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five
years).

____
15
<PAGE>

Other Investment Strategies and Risks

Occasionally, however, securities purchased on a long-term basis may be sold
within 12 months after purchase due to changes in the circumstances of a
particular company or industry, or changes in general market or economic
conditions.

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------

____
16
<PAGE>

Financial Highlights

<TABLE>
<CAPTION>
Liberty Acorn International
Six months Year Ended December 31,
For a share outstanding throughout ended June 30, ------------------------------------------------------
each period 2000 (unaudited) 1999 1998 1997 1996 1995
------------------------------------------------------------------------------------------------------------------------
Class Z Class Z Class Z Class Z Class Z Class Z
------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C> <C>
Net asset value, beginning of period $35.33 $20.82 $18.39 $19.61 $16.59 $15.24
------------------------------------------------------------------------------------------------------------------------

Income from Investment Operations:

Net investment income -- .83 .17 .40 .13 .16
------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain (loss)
on investments, foreign currency and
futures (1.34) 15.45 2.68 (.34) 3.29 1.20
------------------------------------------------------------------------------------------------------------------------
Total from investment
Operations (1.34) 16.28 2.85 .06 3.42 1.36
------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income (.66) (.22) (.15) (.38) (.12) --
------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.51) (1.55) (.27) (.90) (.28) (.01)
------------------------------------------------------------------------------------------------------------------------
Total distributions (1.17) (1.77) (.42) (1.28) (.40) (.01)
------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $32.82 $35.33 $20.82 $18.39 $19.61 $16.59
------------------------------------------------------------------------------------------------------------------------
Total return (a) (3.8)% 79.2% 15.4% 0.2% 20.7% 8.9%
------------------------------------------------------------------------------------------------------------------------

Ratios/supplemental data:

Ratio of expenses to average net
assets 1.06%* 1.11% 1.12% 1.19% 1.17% 1.22%
------------------------------------------------------------------------------------------------------------------------
Ratio of net investment income to
average net assets .01%* .12% .86% .58% .51% .90%
------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 76%* 46% 37% 39% 34% 26%
------------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $2,984 $2,868 $1,725 $1,623 $1,773 $1,276
</TABLE>

(a) Total return is not annualized for periods less than one year.

*Annualized

____
17
<PAGE>

Notes

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____
18
<PAGE>

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________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________

____
19
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You may wish to read the Statement of Additional Information for more
information on the Fund and the securities in which it invests. The Statement
of Additional Information is incorporated into this prospectus by reference,
which means that it is considered to be part of this prospectus.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn International (formerly Acorn International)

[LOGO OF LIBERTY FUNDS]

ALL-STAR.COLONIAL.CRABBE HUSON.NEWPORT.STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (C) 2000
One Financial Center, Boston 02111-2621, 1-800-426-3750
www.libertyfunds.com
<PAGE>

-------------------------------------------------------------------------------
LIBERTY ACORN USA Prospectus, September 29, 2000
-------------------------------------------------------------------------------

Class Z Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Only eligible investors may purchase Class Z shares. See "Your Account -
Eligible Investors" for more information.

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------
T A B L E O F C O N T E N T S
<S> <C>
LIBERTY ACORN USA 2
-----------------
Investment Goal......................................................... 2
Principal Investment Strategies......................................... 2
Principal Investment Risks.............................................. 2
Performance History..................................................... 4
Your Expenses........................................................... 5

MANAGING THE FUND 13
-----------------
Investment Advisor...................................................... 13
Portfolio Manager....................................................... 13

OTHER INVESTMENT
STRATEGIES AND RISKS 14
--------------------
The Information Edge.................................................... 14
Stock Strength Comes
First................................................................... 14
Derivative Strategies................................................... 15
Temporary Defensive
Strategies.............................................................. 15

FINANCIAL HIGHLIGHTS.................................................... 16
--------------------
</TABLE>

Not FDIC May Lose Value
------------------
Insured No Bank Guarantee

___
1

<PAGE>

Liberty Acorn USA

INVESTMENT GOAL
-------------------------------------------------------------------------------

Liberty Acorn USA seeks to provide long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
-------------------------------------------------------------------------------

Liberty Acorn USA invests primarily in stocks of small-and medium-sized U.S.
companies. The Fund generally invests in the stocks of U.S. companies with
capitalizations of less than $2 billion.

The Fund generally invests substantially all of its assets in U.S. companies,
and, under normal market conditions, will invest at least 65% of its assets in
U.S. companies.

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
-------------------------------------------------------------------------------

The principal risks of investing in the Fund are described below. There are many
circumstances (including additional risks that are not described here) that
could prevent the Fund from achieving its investment goal. You may lose money by
investing in the Fund.

__
2
<PAGE>

Liberty Acorn USA

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

__
3
<PAGE>

Liberty Acorn USA

UNDERSTANDING PERFORMANCE

CALENDAR YEAR TOTAL RETURNS show the Fund's Class Z share performance for each
completed calendar year since inception. They include the effects of Fund
expenses.

AVERAGE ANNUAL TOTAL RETURNS are measures of the performance over the past one-
year, three-year and life of the Fund periods. They include the effects of Fund
expenses.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year, three years and life of the Fund. The chart and table
are intended to illustrate some of the risks of investing in the Fund by showing
the changes in the Fund's performance. All returns include the reinvestment of
dividends and distributions. As with all mutual funds, past performance does not
predict the Fund's future performance.

CALENDAR YEAR TOTAL RETURNS
_______________________________________________________________________________

[BAR CHART]

Year Return
---- ------
1997 32.30%
1998 5.79%
1999 23.02%

_______________________________________________________________________________

For period shown in bar chart:
Best quarter: 4th quarter 1999, +18.93%
Worst quarter: 3rd quarter 1998, -19.25%

Average Annual Total Returns -- for periods ended December 31, 1999

Inception Date Life of The
1 Year 3 Years Fund

Class Z 9/4/96 23.02% 19.86% 23.28%
-------------------------------------------------------------------------------
Russell 2000 N/A 21.26% 13.08% 14.65%

__
4
<PAGE>

Liberty Acorn USA

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

Example Expenses help you compare the cost of investing in the Fund to the cost
of investing in other mutual funds. It uses the following hypothetical
conditions:

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

YOUR EXPENSES
-------------------------------------------------------------------------------
Expenses are one of several factors to consider before you invest in a mutual
fund. The tables below describe the fees and expenses you may pay when you buy,
hold and sell shares of the Fund.

Shareholder Fees (paid directly from your investment)

Maximum sales charge (load) on purchases None
_________________________________________________________________
Maximum deferred sales charge (load) on
redemptions None
_________________________________________________________________
Redemption fee (%) (as a percentage of
amount redeemed) None

Annual Fund Operating Expenses (deducted directly from Fund assets)

Management fees/(1)/ (%) .93
_________________________________________________________________
Distribution and service (12b-1) fees (%) None
_________________________________________________________________
Other expenses (%) .22
_________________________________________________________________
Total annual fund operating expenses (%) 1.15
_________________________________________________________________

(1) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

Example Expenses (your actual costs may be higher or lower)

1 Year 3 Years 5 Years 10 Years

$117 $365 $ 633 $1,398

__
5
<PAGE>

Your Account

HOW TO BUY SHARES
-------------------------------------------------------------------------------
If you are an Eligible Investor (described below), your shares will be bought at
the next calculated price after the Fund receives your purchase request in "good
form." "Good form" means that your payment has been received and your
application is complete, including all necessary signatures. The Fund reserves
the right to refuse a purchase order for any reason, including if the Fund
believes that doing so would be in the best interest of the Fund and its
shareholders.

Outlined below are the various options for buying shares:

Method Instructions
-------------------------------------------------------------------------------
By check For new accounts, send a completed application and
(new account) check made payable to the Fund to the transfer agent,
Liberty Funds Services, Inc., P.O. Box 1722, Boston,
MA 02105-1722.
-------------------------------------------------------------------------------
By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your quarterly
statement, or send a letter of instruction including
the Fund name and account number with a check made
payable to the Fund to Liberty Funds Services, Inc.,
P.O. Box 1722, Boston, MA 02105-1722.
-------------------------------------------------------------------------------

By exchange You may acquire shares by exchanging shares you own in
one fund for shares of the same class of shares of the
Fund at no additional cost. There may be an additional
charge if exchanging from a money market fund. To
exchange by telephone, call 1-800-422-3737.
-------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your bank
account to your Fund account. To wire funds to your
Fund account, call 1-800-422-3737 to obtain a control
number and the wiring instructions.
-------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically
transfer (existing transferring money from your bank account to your
account) Fund account by calling 1-800-422-3737. Electronic
funds transfers may take up to two business days to
settle and be considered in "good form." You must set
up this feature prior to your telephone request. Be
sure to complete the appropriate section of the
application.
-------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your Fund
account. You can select a pre-authorized amount to be
sent via electronic funds transfer. Be sure to
complete the appropriate section of the application
for this feature.
-------------------------------------------------------------------------------

By dividend You may automatically invest dividends distributed by
diversification one fund into the same class of shares of the Fund
at no additional sales charge. To invest your
dividends in the Fund, call 1-800-345-6611.
-------------------------------------------------------------------------------
Through an Contact your financial professional. Financial
intermediary professionals may charge fees for their services.

__
6
<PAGE>

Your Account

ELIGIBLE INVESTORS
-------------------------------------------------------------------------------

$1,000 minimum initial investment
---------------------------------

. any shareholder (or family member of such shareholder) who owned shares of
any of the Liberty Acorn Trust funds on September 29, 2000 (when all of the
Trust's then outstanding shares were re-designated Class Z shares) and who
has since then continued to own shares of any funds distributed by Liberty
Funds Distributor, Inc.;

. any trustee of Liberty Acorn Trust, any employee of Liberty WAM, or a
member of the family of the Employee; and

. any person or entity listed in the account registration for any account
(such as joint owners, trustees, custodians, and designated beneficiaries)
that held shares of any of the funds of Liberty Acorn Trust on September
29, 2000 and that has continued to held shares of any funds distributed by
Liberty Funds Distributor, Inc.

$100,000 minimum initial investment
----------------------------------

. any client of a broker-dealer or registered investment advisor that
recommends Fund shares and charges an asset-based fee;

. any insurance company, trust company or bank, which is purchasing shares
for its own account;

. any endowment, investment company or foundation; and

. any client of an investment advisory affiliate of the distributor if the
client meets certain criteria established by the distributor and its
affiliate.

No minimum initial investment
-----------------------------
. any retirement plan with aggregate assets of at least $5 million at the
time it purchases Class Z shares and which is purchasing shares directly
from the distributor or through a third party broker-dealer; and

If you have any questions about your eligibility to purchase Class Z shares of
the Fund, please call 800-345-6611. If you hold Fund shares through a broker-
dealer or other financial institution, you eligibility to purchase Class Z
shares may differ depending on that institution's policies.

____
7
<PAGE>

Your Account

CHOOSING A SHARE CLASS

The Fund offers one class of shares in this prospectus -- Class Z.

The Fund also offers three additional classes of shares -- Class A, B and C
shares are available through a separate prospectus. Each share class has its own
sales charge and expense structure. Determining which share class is best for
you depends on the dollar amount you are investing and the number of years for
which you are willing to invest. Based on your personal situation, your
investment advisor can help you decide which class of shares makes the most
sense for you. In general, anyone who is eligible to purchase Class Z shares,
which do not incur Rule 12b-1 fees or sales charges, should do so in preference
over other classes.

PRICE OF FUND SHARES
-------------------------------------------------------------------------------

HOW TO EXCHANGE SHARES
-------------------------------------------------------------------------------

HOW TO SELL SHARES
-------------------------------------------------------------------------------
You may sell shares of the Fund on any regular business day that the New York
Stock Exchange (NYSE) is open.

__
8
<PAGE>

Your Account

Outlined below are the various options for selling shares:

Method Instructions
-------------------------------------------------------------------------------
By exchange You may sell shares by exchanging from the Fund into Class Z
shares or Class A shares of another fund at no additional
cost. To exchange by telephone, call 1-800-422-3737.
-------------------------------------------------------------------------------
By telephone You or your financial advisor may sell shares by telephone
and request that a check be sent to your address of record by
calling 1-800-422-3737, unless you have notified the Fund of
an address change within the previous 30 days. The dollar
limit for telephone sales is $100,000 in a 30-day period. You
do not need to set up this feature in advance of your call.
Certain restrictions apply to retirement accounts. For
details, call 1-800-345-6611.
-------------------------------------------------------------------------------
By mail You may send a signed letter of instruction or stock power
form to the address below. In your letter of instruction,
note the Fund's name, share class, account number, and the
dollar value or number of shares you wish to sell. All
account owners must sign the letter, and signatures must be
guaranteed by either a bank, a member firm of a national
stock exchange or another eligible guarantor institution.
Additional documentation is required for sales by
corporations, agents, fiduciaries, surviving joint owners and
individual retirement account owners. For details, call
1-800-345-6611.

Systematic You may automatically sell a specified dollar amount or
Withdrawal Plan percentage on a monthly, quarterly or semiannual basis if
your account balance is at least $5,000 and have the proceeds
sent to you. This feature is not available if you hold your
shares in certificate form. Be sure to complete the
appropriate section of the account application for this
feature.
-------------------------------------------------------------------------------
Through an Contact your financial professional. Financial professionals
Intermediary may charge fees for their services.

FUND POLICY ON TRADING OF FUND SHARES

-------------------------------------------------------------------------------
The Fund does not permit short-term or excessive trading. Excessive purchases,
redemptions or exchanges of Fund shares disrupt portfolio management and drive
Fund expenses higher. In order to promote the best interests of the Fund, the
Fund reserves the right to reject any purchase or order exchange request,
particularly from market timers or investors who, in the advisor's opinion, have
a pattern of short-term or excessive trading or whose trading has been or may be
disruptive to the Fund. The fund into which you would like to exchange also may
reject your request.

____
9
<PAGE>

Your Account

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------

Share Certificates Share certificates are not available for Class Z shares.

____
10
<PAGE>

Your Account

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities held
by the Fund, net of expenses incurred by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of securities
held for more than 12 months and net short-term capital
gains, which are gains on sales of securities held for a 12-
month period or less.

Distribution Options. The Fund distributes dividends in June and December and
any capital gains (including short-term capital gains) at least annually. You
can choose one of the options listed in the table below for these distributions
when you open your account. To change your distribution option call
1-800-345-6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
--------------------------------------------------------------------------------

. send the check to your address of record

. send the check to a third party address

. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

Tax Consequences Regardless of whether you receive your distributions in cash
or reinvest them in additional Fund shares, all Fund distributions are subject
to federal income tax. Depending on the state where you live, distributions may
also be subject to state and local income taxes.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on federal, state, local or other applicable tax
laws.

____
11
<PAGE>

Your Account

____
12
<PAGE>

Managing the Fund

INVESTMENT ADVISOR
--------------------------------------------------------------------------------

Liberty Wanger Asset Management (Liberty WAM) (formerly Wanger Asset Management,
L.P. (WAM)), located at 227 West Monroe Street, Suite 3000, Chicago, Illinois
60606, is the Fund's investment advisor. Liberty WAM and its predecessor have
managed mutual funds, including the Fund, since 1992. In its duties as
investment advisor, Liberty WAM runs the Fund's day-to-day business, including
placing all orders for the purchase and sale of the Fund's portfolio securities.
As of June 30, 2000, Liberty WAM managed over $9 billion in assets.

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.93% of the Fund's
average daily net assets. Liberty WAM also receives an administrative fee from
the Fund at the annual rate of .05% of the Fund's average daily net assets.

PORTFOLIO MANAGER
--------------------------------------------------------------------------------

Robert A. Mohn

Lead portfolio manager

Robert Mohn is a vice president of Liberty Acorn Trust He has been a member of
the domestic analytical team at Liberty WAM and WAM since 1992, and was a
principal of WAM from 1995 to September 29, 2000. He has managed Liberty Acorn
USA since its inception in 1996, and also manages a mutual fund underlying
variable insurance products and the U.S. portfolio of an investment company
whose shares are offered only to non-U.S. investors. He is a CFA and holds a BS
from Stanford University and an MBA from the University of Chicago.

____
13
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

THE INFORMATION EDGE
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock price
. innovative marketing . adequate working relative to growth
. managerial skill capital potential
. market niche . conservative . valuable assets
. good earnings accounting practices
prospects . adequate profit
. strong demand margin
for product

The realization of this A strong balance sheet Once Liberty WAM uncovers
growth potential would gives management greater an attractive company, it
likely produce superior flexibility to pursue identifies a price that
performance that is strategic objectives and it believes would also
sustainable over time. is essential to make the stock a good
maintaining a competitive value.
advantage.
--------------------------------------------------------------------------------
</TABLE>

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

____
14
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------

TEMPORARY DEFENSIVE STRATEGIES
-------------------------------------------------------------------------------

Financial Highlights

The financial highlights table is intended to help you understand the Fund's
financial performance. Information is shown for the Fund's Class Z shares since
inception. The Fund's fiscal year runs from January 1 to December 31. Certain
information reflects financial results for a single Fund share. The total
returns in the table represent the rate that you would have earned (or lost) on
an investment in the Fund (assuming reinvestment of all dividends and
distributions). The information with respect to the six month period ended June
30, 2000 is unaudited. The information for the three years ended December 31,
1999 and the period ended December 31, 1996 is audited. For periods up to and
including the year ended 1999, this information has been derived from the Fund's
financial statements which have been audited by Ernst & Young LLP, independent
auditors, whose report, along with the Fund's audited financial statements, is
included in the Fund's annual report. You can request a free annual report by
calling 1-800-426-3750.

Liberty Acorn USA

<TABLE>
<CAPTION> Six months
For a share outstanding ended June 30, 2000 Year Ended December 31, Inception 9/4/96
throughout each period (unaudited) 1999 1998 1997 Through 12/31/96
------------------------------------------------------------------------------------------------------------------------------------
Class Z Class Z Class Z Class Z Class Z
------------------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C>
Net asset value, beginning of period $ 16.75 $ 14.80 $ 15.12 $ 11.65 $ 10.00
------------------------------------------------------------------------------------------------------------------------------------
Income from Investment
Operations:

Net investment loss (a) (.02) -- (.07) (.07) (.02)
------------------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on
investments (2.67) 3.32 .87 3.83 1.67
------------------------------------------------------------------------------------------------------------------------------------
Total from investment
operations (2.69) 3.32 .80 3.76 1.65
------------------------------------------------------------------------------------------------------------------------------------
Less distributions:
Dividends from net investment income -- -- -- -- --
------------------------------------------------------------------------------------------------------------------------------------
Distributions from net realized and
unrealized gains reportable for federal
income taxes (.32) (1.37) (1.12) (.29) --
------------------------------------------------------------------------------------------------------------------------------------
Total distributions (.32) (1.37) (1.12) (.29) --
------------------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $ 13.74 $ 16.75 $ 14.80 $ 15.12 $ 11.65
------------------------------------------------------------------------------------------------------------------------------------
Total return (c) (16.1)% 23.0% 5.8% 32.3% 16.5%
------------------------------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net
assets (b) 1.13%* 1.15% 1.20% 1.35% 1.85%*
------------------------------------------------------------------------------------------------------------------------------------
Ratio of net investment loss to average
net assets (.27%)* 0.00% (.42%) (.49%) (.99%)*
------------------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 65%* 49% 42% 33% 20%*
------------------------------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 305 $ 371 $ 281 $ 185 $ 53
</TABLE>

(a) Net investment loss per share was based upon the average shares outstanding
during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the ratio of expenses to average net assets for Liberty Acorn USA reflects
gross custodian fees. This ratio net of custodian fees paid indirectly would
have been 1.79% for the period ended December 31, 1996.

*Annualized

____
16
<PAGE>

Notes

--------------------------------------------------------------------------------

____
17
<PAGE>

--------------------------------------------------------------------------------

____
18
<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You may wish to read the Statement of Additional Information for more
information on the Fund and the securities in which it invests. The Statement
of Additional Information is incorporated into this prospectus by reference,
which means that it is considered to be part of this prospectus.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust: (formerly Acorn Investment Trust) 811-01829

. Liberty Acorn USA (formerly Acorn USA)

[LOGO OF LIBERTY FUNDS]

ALL - STAR . COLONIAL . CRABBE HUSON, NEWPORT . STEIN ROE ADVISOR
Liberty Funds Distributor, Inc.(C) 2000
One Financial Center, Boston, MA 02111-2621, 1-800-426-3750
www.libertyfunds.com

<PAGE>

LIBERTY ACORN FOREIGN FORTY Prospectus, September 29, 2000

Class Z Shares

Advised by Liberty Wanger Asset Management, L.P.

Liberty Acorn Trust

Only eligible investors may purchase Class Z shares. See "Your Account -
Eligible Investors" for more information.

Although these securities have been registered with the Securities and Exchange
Commission, the Commission has not approved or disapproved any shares offered in
this prospectus or determined whether this prospectus is truthful or complete.
Any representation to the contrary is a criminal offense.

-------------------------------------------------------------------------------
T A B L E O F C O N T E N T S

<TABLE>
<CAPTION>
<S> <C>
Liberty Acorn Foreign Forty 2
---------------------------
Investment Goal............................................................ 2
Principal Investment Strategies............................................ 2
Principal Investment Risks................................................. 2
Performance History........................................................ 4
Your Expenses.............................................................. 5

YOUR ACCOUNT 6
------------
How to Buy Shares.......................................................... 6
Eligible Investors......................................................... 7
Price of Fund Shares....................................................... 8
How to Exchange Shares..................................................... 8
How to Sell Shares......................................................... 8
Fund Policy on Trading of Fund Shares...................................... 9
Other Information About Your Account....................................... 10

MANAGING THE FUND 13
-----------------
Investment Advisor......................................................... 13
Portfolio Managers......................................................... 13

OTHER INVESTMENT
STRATEGIES AND RISKS 15
--------------------
The Information Edge....................................................... 15
Stock Strength Comes First................................................. 15
Derivative Strategies...................................................... 16
Temporary Defensive Strategies............................................. 16

FINANCIAL HIGHLIGHTS 17
--------------------
</TABLE>

Not FDIC May Lose Value
-----------------
Insured No Bank Guarantee
____
1
<PAGE>

Liberty Acorn Foreign Forty

INVESTMENT GOAL
-------------------------------------------------------------------------------
Liberty Acorn Foreign Forty seeks long-term growth of capital.

PRINCIPAL INVESTMENT STRATEGIES
-------------------------------------------------------------------------------

Liberty Acorn Foreign Forty is an international fund and invests the majority of
its assets in the stocks of foreign companies based in developed markets outside
the U.S.

Additional strategies that are not principal investment strategies and the risks
associated with them are described below under "Other Investment Strategies and
Risks."

PRINCIPAL INVESTMENT RISKS
-------------------------------------------------------------------------------
The principal risks of investing in the Fund are described below. There are
many circumstances (including additional risks that are not described here) that
could prevent the Fund from achieving its investment goal. You may lose money
by investing in the Fund.

____
2
<PAGE>

Liberty Acorn Foreign Forty

day-to-day and may underperform other asset classes over an extended period of
time. Individual companies may report poor results or be negatively affected by
industry and/or economic trends and developments. The prices of securities
issued by such companies may suffer a decline in response. These price movements
may result from factors affecting individual companies, industries or the
securities market as a whole.

Sector risk may sometimes be present in the Fund's investments. Companies that
are in different but closely related industries are sometimes described as being
in the same broad economic sector. The values of stock of many different
companies in a market sector may be similarly affected by particular economic or
market events. Although the Fund does not intend to focus on any particular
sector, at times, the Fund may have a significant portion of its assets invested
in a particular sector. An example of a sector in which the Fund may sometimes
have a significant portion of its assets invested is technology. Technology
companies may be significantly affected by falling prices and profits, and
intense competition. In addition, the rate of technological change for
technology companies is generally higher than for other companies, often
requiring extensive and sustained investment in research and development, and
exposing such companies to the risk of rapid product obsolescence. The price of
many technology stocks has risen based on projections of future earnings and
company growth. If a company does not perform as expected, the price of the
stock could decline significantly. Many technology companies are currently
operating at a loss and may never be profitable.

An investment in the Fund is not a deposit in a bank and is not insured or
guaranteed by the Federal Deposit Insurance Corporation or any other government
agency.

____
3
<PAGE>

Liberty Acorn Foreign Forty

UNDERSTANDING PERFORMANCE

Calendar year total returns show the Fund's Class Z share performance for each
completed calendar year since inception. They include the effects of Fund
expenses.

Average annual total returns are measures of the Fund's performance over the
past one-year and life of the Fund periods. They include the effects of Fund
expenses.

The Fund's returns are compared to the SSB World ex-U.S. Cap Range $2-10 Billion
Index. The SSB World ex-U.S. Cap Range $2-10 Billion Index is Salomon Smith
Barney's two to ten billion U.S. dollar security market subset of its Broad
Market Index. It represents a midcap developed market index, excluding the U.S.
Unlike the Fund, an index is not an investment, does not incur fees or expenses
and is not professionally managed. It is not possible to invest directly in an
index.

PERFORMANCE HISTORY
--------------------------------------------------------------------------------

The bar chart below shows changes in the Fund's performance from year to year by
illustrating the Fund's calendar year total returns for its Class Z shares. The
performance table following the bar chart shows how the Fund's average annual
returns for Class Z shares compare with those of broad measures of market
performance for one year and life of the Fund. The chart and table are intended
to illustrate some of the risks of investing in the Fund by showing the changes
in the Fund's performance. All returns include the reinvestment of dividends and
distributions. Performance results include the effect of expense reduction
arrangements. If these arrangements were not in place, then performance would
have been lower. Any expense reduction arrangements may be discounted at any
time. As with all mutual funds, past performance does not predict the Fund's
future performance.

Calendar Year Total Returns/(1)/

--------------------------------------------------------------------------------
[Bar Chart]

Year Return
---- ------
1999 81.60%

--------------------------------------------------------------------------------

For period shown in bar chart: Best quarter: 4th quarter 1999, +46.65%
Worst quarter: 3rd quarter 1999, +3.90%

Average Annual Total Returns -- for periods ended December 31, 1999/(1)/

Inception Date 1 Year Life of the Fund

Class Z 11/23/98 81.60% 86.84%
-------------------------------------------------------------------------------

SSB Cap Range $2-10B N/A 23.52% 24.72%

(1) The Fund's performance during 1999 was achieved in a period of unusual
market conditions that are unlikely to continue.

____
4
<PAGE>

Liberty Acorn Foreign Forty

UNDERSTANDING EXPENSES

Annual Fund Operating Expenses are deducted from the Fund. They include
management and administration fees, and administrative costs including pricing
and custody services.

. $10,000 initial investment

. 5% total return for each year

. fund operating expenses remain the same

. assumes reinvestment of all dividends and distributions

Shareholder Fees (paid directly from your investment)

Maximum sales charge (load) on purchases None
-----------------------------------------------------------------
Maximum deferred sales charge (load) on
redemptions None
-----------------------------------------------------------------
Redemption fee (%) (as a percentage of
amount redeemed) None

Annual Fund Operating Expenses (deducted directly from Fund assets)

Management fees/(2)/ (%) .95
-----------------------------------------------------------------
Distribution and service (12b-1) fees (%) None
-----------------------------------------------------------------
Other expenses (%) .62
-----------------------------------------------------------------
Total annual fund operating expenses/(3)/ (%) 1.57
-----------------------------------------------------------------

(2) In addition to the management fee, the Fund pays the Advisor an
administrative fee of .05%, which is included in "Other Expenses."

(3) The Fund's advisor has voluntarily agreed to reimburse the Fund for any
ordinary operating expenses (exclusive of distribution and service fees,
interest, taxes and extraordinary expenses, if any) exceeding 1.45% of the
average annual net assets for Class Z. This arrangement may be modified or
terminated by either the Fund or its advisor on 30 days' notice to the
other. As a result, the actual total annual fund operating expenses for
Class Z would be 1.45%.

Example Expenses (your actual costs may be higher or lower)

1 Year 3 Years 5 Years 10 Years

$160 $496 $ 855 $1,867

____
5
<PAGE>

Your Account

Outlined below are the various options for buying shares:

Method Instructions
-------------------------------------------------------------------------------
By check For new accounts, send a completed application and
(new account) check made payable to the Fund to the transfer
agent, Liberty Funds Services, Inc., P.O. Box
1722, Boston, MA 02105-1722.
-------------------------------------------------------------------------------
By check For existing accounts, fill out and return the
(existing account) additional investment stub included in your
quarterly statement, or send a letter of
instruction including the Fund name and account
number with a check made payable to the Fund to
Liberty Funds Services, Inc., P.O. Box 1722,
Boston, MA 02105-1722.
-------------------------------------------------------------------------------

By exchange You may acquire shares by exchanging shares you own
in one fund for shares of the same class of the
Fund at no additional cost. There may be an
additional charge if exchanging from a money market
fund. To exchange by telephone, call 1-800-422-
3737.
-------------------------------------------------------------------------------
By wire You may purchase shares by wiring money from your
bank account to your Fund account. To wire funds to
your Fund account, call 1-800-422-3737 to obtain a
control number and the wiring instructions.
-------------------------------------------------------------------------------
By electronic funds You may purchase shares by electronically
transfer (existing transferring money from your bank account to your
account) Fund account by calling 1-800-422-3737. Electronic
funds transfers may take up to two business days to
settle and be considered in "good form." You must
set up this feature prior to your telephone
request. Be sure to complete the appropriate
section of the application.
-------------------------------------------------------------------------------
Automatic You can make monthly or quarterly investments
investment plan automatically from your bank account to your fund
account. You can select a pre-authorized amount to
be sent via electronic funds transfer. Be sure to
complete the appropriate section of the application
for this feature.
-------------------------------------------------------------------------------

By dividend You may automatically invest dividends distributed
diversification by one fund into the same class of shares of the
Fund at no additional sales charge. To invest your
dividends in the Fund, call 1-800-345-6611.
-------------------------------------------------------------------------------
Through an Contact your financial professional. Financial
intermediary professionals may charge fees for their services.

____
6
<PAGE>

ELIGIBLE INVESTORS

Only Eligible investors may purchase Class Z shares of the Fund, directly or by
exchange. Eligible Investors are subject to different minimum investment
requirements. Eligible Investors and their applicable investment minimums are:

$1,000 minimum initial investment
---------------------------------

. any trustee of Liberty Acorn Trust, any employee of Liberty WAM, or a
member of the family of the trustee or employee; and

$100,000 minimum initial investment
-----------------------------------

. any client of a broker-dealer or registered investment advisor that
recommends Fund shares and charges an asset-based fee;

. any insurance company, trust company or bank, which is purchasing shares
for its own account;

. any endowment, investment company or foundation; and

. any client of an investment advisory affiliate of the distributor if the
client meets certain criteria established by the distributor and its
affiliate.

No minimum initial investment
-----------------------------

. any person investing all or part of the proceeds of a distribution,
"roll over" or transfer assets into a Liberty IRA from any deferred
compensation plan which was a shareholder of any of the Liberty Acorn Funds
on September 29, 2000, in which the investor was a participant and through
which the investor invested in one or more of the Liberty Acorn Funds
immediately prior to the distribution, transfer or roll over; and

The Fund reserves the right to change the criteria for eligible investors and
these investment minimums. No minimum investment applies to accounts
participating in the automatic investment plan.

The Fund also reserves the right to refuse a purchase order for any reason,
including if it believes that doing so would be in the best interest of the Fund
and its shareholders.

----
7
<PAGE>

CHOOSING A SHARE CLASS

The Fund offers one class of shares in this prospectus -- Class Z.

PRICE OF FUND SHARES
--------------------------------------------------------------------------------

HOW TO EXCHANGE SHARES
--------------------------------------------------------------------------------

____
8
<PAGE>

Outlined below are the various options for selling shares:

By mail You may send a signed letter of instruction or stock power
form to the address below. In your letter of instruction,
note the Fund's name, share class, account number, and the
dollar value or number of shares you wish to sell. All
account owners must sign the letter, and signatures must be
guaranteed by either a bank, a member firm of a national
stock exchange or another eligible guarantor institution.
Additional documentation is required for sales by
corporations, agents, fiduciaries, surviving joint owners and
individual retirement account owners. For details, call
1-800-345-6611.

Mail your letter of instruction to Liberty Funds Services,
Inc., P.O. Box 1722, Boston, MA 02105-1722.
--------------------------------------------------------------------------------
By wire You may sell shares and request that the proceeds be wired to
your bank. You must set up this feature prior to your
telephone request. Be sure to complete the appropriate
section of the account application for this feature.
--------------------------------------------------------------------------------
By electronic You may sell shares and request that the proceeds be
funds transfer electronically transferred to your bank. Proceeds may take
up to two business days to be received by your bank. You must
set up this feature prior to your request. Be sure to
complete the appropriate section of the account application
for this feature.
--------------------------------------------------------------------------------
Systematic You may automatically sell a specified dollar amount or
Withdrawal Plan percentage on a monthly, quarterly or semiannual basis if
your account balance is at least $5,000 and have the proceeds
sent to you. This feature is not available if you hold your
shares in certificate form. Be sure to complete the
appropriate section of the account application for this
feature.
-------------------------------------------------------------------------------
Through an Contact your financial professional. Financial professionals
Intermediary may charge fees for their services.

FUND POLICY ON TRADING OF FUND SHARES
-------------------------------------------------------------------------------
The Fund does not permit short-term or excessive trading. Excessive purchases,
redemptions or exchanges of Fund shares disrupt portfolio management and drive
Fund expenses higher. In order to promote the best interests of the Fund, the
Fund reserves the right to reject any purchase order or exchange request,
particularly from market timers or investors who, in the advisor's opinion, have
a pattern of short-term or excessive trading or whose trading has been or may be
disruptive to the Fund. The fund into which you would like to exchange also may
reject your request.

____
9
<PAGE>

OTHER INFORMATION ABOUT YOUR ACCOUNT
--------------------------------------------------------------------------------
How the Fund's Share Price is Determined The price of a Fund's Class Z shares
is its net asset value. The net asset value is determined at the close of
regular trading on the NYSE, usually 4:00 p.m. Eastern time, on each business
day that the NYSE is open (typically Monday through Friday).

The Fund determines its net asset value for its Class Z shares by dividing total
net assets attributable to Class Z shares by the number of outstanding Class Z
shares. In determining the net asset value, the Fund must determine the price
of each security in its portfolio at the close of each trading day. Because the
Fund holds securities that are traded on foreign exchanges, the value of these
securities may change on days when shareholders will not be able to buy or sell
Fund shares. This will affect the Fund's net asset value on the day it is next
determined. Securities for which market quotations are available are valued each
day at the current market value. However, where market quotations are not
available, or when the advisor believes that subsequent events have made them
unreliable, the Fund may use other data to determine the fair value of the
securities.

Share Certificates Share certificates are not available for Class Z shares.

____
10
<PAGE>

UNDERSTANDING FUND DISTRIBUTIONS

Dividends, Distributions, and Taxes The Fund has the potential to make the
following distributions:

Types of Distributions

Dividend Represents interest and dividends earned from securities
held by the Fund.
--------------------------------------------------------------------------------
Capital gains Represents net long-term capital gains on sales of
securities held for more than 12 months and net short-term
capital gains, which are gains on sales of securities held
for a 12-month period or less.

Distribution Options. Normally, the Fund distributes dividends in June and
December and any capital gains (including short-term capital gains) at least
annually. You can choose one of the options listed in the table below for these
distributions when you open your account. To change your distribution option
call 1-800-345-6611.

If you do not indicate on your application your preference for handling
distributions, the Fund will automatically reinvest all distributions in
additional shares of the Fund.

Distribution Options

Reinvest all distributions in additional shares of the Fund
--------------------------------------------------------------------------------

Reinvest all distributions in shares of another fund
--------------------------------------------------------------------------------

Receive dividends in cash (see options below) and reinvest capital gains
--------------------------------------------------------------------------------

Receive all distributions in cash (with one of the following options):

. send the check to your address of record
. send the check to a third party address
. transfer the money to your bank via electronic funds transfer

Distributions of $10 or less will automatically be reinvested in additional Fund
shares. If you elect to receive distributions by check and the check is returned
as undeliverable, or if you do not cash a distribution check within six months
of the check date, the distribution will be reinvested in additional shares of
the Fund.

In general, any distributions of dividends, interest and short-term capital
gains are taxable as ordinary income. Distributions of long-term capital gains
are generally taxable as such, regardless of how long you have held your Fund
shares. You will be provided with information each year regarding the amount of
ordinary income and capital gains distributed to you for the previous year and
any portion of your distribution which is exempt from state and local taxes.
Your investment in the Fund may have additional personal tax implications.
Please consult your tax advisor on foreign, federal, state, local or other
applicable tax laws.

____
11
<PAGE>

____
12
<PAGE>

Managing the Fund

Liberty WAM's advisory fee for managing the Fund in 1999 was 0.95% of the Fund's
average daily net assets. Liberty WAM also receives an administrative fee from
the Fund at the annual rate of .05% of the Fund's average daily net assets.

Marcel P. Houtzager
Co-portfolio manager

Marcel Houtzager is a vice president of Liberty Acorn Trust, and has managed
Liberty Acorn Foreign Forty since its inception in 1998. He has been a member
of the international analytical team at Liberty WAM and WAM since 1992, and was
a principal of WAM from 1995 to September 29, 2000. Mr. Houtzager also manages
an international mutual fund underlying variable insurance products and the
foreign portfolio of an investment company whose shares are offered only to non-
U.S. investors. He is a CFA and a CPA, and earned his BA from Pomona College and
his MBA from the University of California at Berkeley.

____
13
<PAGE>

Managing the Fund

Roger D. Edgley
Co-portfolio manager

____
14
<PAGE>

Other Investment Strategies and Risks

UNDERSTANDING THE FUND'S OTHER INVESTMENT STRATEGIES AND RISKS

THE INFORMATION EDGE
--------------------------------------------------------------------------------

The Fund invests in entrepreneurially managed smaller, mid-sized
and larger companies that it believes are not as well known by financial
analysts and whose domination of a niche creates the opportunity for superior
earnings-growth potential. Liberty WAM may identify what it believes are
important economic, social or technological trends (for example, the growth of
out-sourcing as a business strategy, or the productivity gains from the
increasing use of technology) and try to identify companies it thinks will
benefit from those trends.

<TABLE>
<CAPTION>
Growth Potential Financial Strength Fundamental Value
--------------------------------------------------------------------------------
<S> <C> <C>
. superior technology . low debt . reasonable stock price
. innovative . adequate working relative to growth
marketing capital potential
. managerial skill . conservative . valuable assets
. market niche accounting practices
. good earnings . adequate profit margin
prospects
. strong demand
for product

STOCK STRENGTH COMES FIRST
--------------------------------------------------------------------------------
Liberty WAM's analysts continually screen companies and make more than 1,000
face-to-face visits around the globe each year. To accomplish this, Liberty WAM
analysts talk to top management, vendors, suppliers and competitors, whenever
possible.

In managing the Fund, Liberty WAM tries to maintain lower taxes and transaction
costs by investing with a long-term time horizon (at least two to five years).
However,

____
15
<PAGE>

Other Investment Strategies and Risks

DERIVATIVE STRATEGIES
--------------------------------------------------------------------------------
The Fund may enter into a number of hedging strategies, including those that
employ futures and options, to gain or reduce exposure to particular securities
or markets. These strategies, commonly referred to as derivatives, involve the
use of financial instruments whose values depend on, or are derived from, the
value of an underlying security, index or currency. The Fund may use these
strategies to adjust the Fund's sensitivity to changes in interest rates or for
other hedging purposes (i.e., attempting to offset a potential loss in one
position by establishing an interest in an opposite position). Derivative
strategies involve the risk that they may exaggerate a loss, potentially losing
more money than the actual cost of the underlying security, or limit a potential
gain. Also, with some derivative strategies there is a risk that the other party
to the transaction may fail to honor its contract terms, causing a loss to the
Fund.

TEMPORARY DEFENSIVE STRATEGIES
--------------------------------------------------------------------------------
At times, Liberty WAM may determine that adverse market conditions make it
desirable to temporarily suspend the Fund's normal investment activities. During
such times, the Fund may, but is not required to, invest in cash or high-
quality, short-term debt securities, without limit. Taking a temporary defensive
position may prevent the Fund from achieving its investment goal.

____
16
<PAGE>

Financial Highlights

The financial highlights tables are intended to help you understand the Fund's
financial performance. Information is shown for the Fund's Class Z shares since
inception. The Fund's fiscal year runs from January 1 to December 31. Certain
information reflects financial results for a single Fund share. The total
returns in the table represent the rate that you would have earned (or lost) on
an investment in the Fund (assuming reinvestment of all dividends and
distributions). The information with respect to the six month period ended June
30, 2000 is unaudited. The information with respect to the year ended December
31, 1999 and the period ended December 31, 1998 is audited. For periods up to
and including the year ended 1999, this information has been derived from the
Fund's financial statements which have been audited by Ernst & Young LLP,
independent auditors, whose report, along with the Fund's audited financial
statements, is included in the Fund's annual report. You can request a free
annual report by calling 1-800-426-3750.

<TABLE>
<CAPTION>
Liberty Acorn Foreign Forty
--------------------------------------------------------------------------------------------------------------
Six months
ended 6/30/00 Year Ended Inception 11/23/98
(unaudited) 12/31/99 Through 12/31/98
<S> <C> <C> <C>
--------------------------------------------------------------------------------------------------------------
For a share outstanding throughout each period
--------------------------------------------------------------------------------------------------------------
Class Z Class Z Class Z
--------------------------------------------------------------------------------------------------------------
Net asset value, beginning of period $ 19.93 $ 11.00 $ 10.00
--------------------------------------------------------------------------------------------------------------
Income from Investment Operations:

Net investment loss (a) -- (.02) (.01)
--------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain (loss) on
investments (.12) 8.98 1.01
--------------------------------------------------------------------------------------------------------------
Total from investment operations (.12) 8.96 1.00
--------------------------------------------------------------------------------------------------------------
Less Distributions:
Dividends from net investment income (.03) -- --
Distributions from net realized and unrealized
gains reportable for federal income taxes (.11) (.03) --
Total Distributions (.14) (.03) --
--------------------------------------------------------------------------------------------------------------
Net asset value, end of period $ 19.67 $ 19.93 $ 11.00
--------------------------------------------------------------------------------------------------------------
Total return (d) (0.6%) 81.6% 10.0%
--------------------------------------------------------------------------------------------------------------
Ratios/supplemental data:

Ratio of expenses to average net assets (b)(c) 1.37%* 1.48% 1.73%*
--------------------------------------------------------------------------------------------------------------
Ratio of net investment loss to average net
assets (c) (.03%)* (.17%) (.78%)*
--------------------------------------------------------------------------------------------------------------
Portfolio turnover rate 74%* 60% 90%*
--------------------------------------------------------------------------------------------------------------
Net assets at end of period
(in millions) $ 144 $ 107 $ 16
</TABLE>

(a) Net investment loss per share was based upon the average shares outstanding
during the period.

(b) In accordance with a requirement by the Securities and Exchange Commission,
the expense ratio reflects total expenses prior to the reduction of
custodian fees for cash balances it maintains with the custodian
("custodian fees paid indirectly"). This ratio net of custodian fees paid
indirectly would have been 1.45% for the period ended December 31, 1998,
and the year ended December 31, 1999.

(d) Total return is not annualized for periods less than one year.

*Annualized

____
17
<PAGE>

Notes

_______________________________________________________________________________
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_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________

____
18

<PAGE>

FOR MORE INFORMATION
--------------------------------------------------------------------------------

You can get more information about the Fund's investments in the Fund's semi-
annual and annual reports to shareholders. The annual report contains a
discussion of the market conditions and investment strategies that significantly
affected the Fund's performance over its last fiscal year.

You can get free copies of reports and the Statement of Additional Information,
request other information and discuss your questions about the Fund by writing
or calling the Fund's distributor at:

Liberty Funds Distributor, Inc.
One Financial Center
Boston, MA 02111-2621
1-800-426-3750
www.libertyfunds.com

Text-only versions of all Fund documents can be viewed online or downloaded from
the Edgar database on the Securities and Exchange Commission internet site at
www.sec.gov.

Public Reference Room
Securities and Exchange Commission
Washington, DC 20549-0102

Information on the operation of the Public Reference Room may be obtained by
calling 1-202-942-8090.

Investment Company Act file number:

Liberty Acorn Trust (formerly Acorn Investment Trust): 811-01829

. Liberty Acorn Foreign Forty (formerly Acorn Foreign Forty)

--------------------------------------------------------------------------------
[LOGO] [LIBERTY FUNDS]

ALL STAR . COLONIAL . CRABBE HUSON . NEWPORT . STEIN ROE ADVISOR

Liberty Funds Distributor, Inc. (C) 2000
One Financial Center, Boston, MA 02111-2621, 1-800-426-3750
www.libertyfunds.com