ACORN INVESTMENT TRUST
497, 1999-05-05
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<PAGE>
 
              The Acorn Family of Funds


              Acorn Fund
              Acorn International
              Acorn USA
              Acorn Twenty
              Acorn Foreign Forty


              100% No-Load Funds




              Prospectus

              May 1, 1999


The Securities and Exchange Commission has not approved or disapproved these
securities or passed upon the adequacy of this prospectus. Any representation to
the contrary is a criminal offense.
<PAGE>










 
              Acorn Investment Trust
              227 West Monroe Street
              Suite 3000
              Chicago, Illinois 60606
              1-800-9-ACORN-9 (1-800-922-6769)
<PAGE>

<TABLE>
<CAPTION>


Contents
- ---------------------------------------------------------------------------------------------------
<S>             <C>                     <C>                          <C>

      2         At a Glance             Acorn Fund                    2
                Fund Objective, Risks,  Acorn International           4
                Fees and Expenses       Acorn USA                     6
                                        Acorn Twenty                  8
                                        Acorn Foreign Forty          10
- ---------------------------------------------------------------------------------------------------

      12        Management of           Portfolio Managers
                the Funds               Management Fees

      14        How the Funds Invest    The Acorn Investment Philosophy
                                        Securities in which the Funds Invest and Risks
                                        Managing Risk
                                        Year 2000

      18        Your Account            Doing Business with Acorn
                                        Choices for Your Account Registration
                                        How to Buy Shares
                                        How to Sell Shares
                                        Signature Guarantee

      23        Shareholder and         Statements and Reports
                Account Policies        Share Price
                                        Address Changes
                                        General Information Pertaining to all Telephone Transactions
                                        Telephone Exchange Plan and Money Market Funds
                                        Exchange Plan Restrictions
                                        Authorized Agents

      26        Dividends, Capital      Distribution Options
                Gains and Taxes         Taxes
                                        Foreign Income Taxes

      27        Fund Service Providers  Transfer Agent and Custodian
                                        Distributor

      28        Financial Highlights    Acorn Fund
                                        Acorn International
                                        Acorn USA
                                        Acorn Twenty
                                        Acorn Foreign Forty
</TABLE>

<PAGE>

AT A GLANCE          Acorn Fund 



Fund Objective

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

Investment Strategy

Acorn Fund is a diversified mutual fund that invests primarily in the stocks of
small- and medium-size companies. The fund generally invests in the stocks of
companies around the globe with capitalizations of less than $1 billion with the
intention of holding them as they grow and selling them when they become large.

The fund believes that these smaller, less profiled companies may offer higher
return potential than the stocks of large companies.

Acorn Fund typically looks for the stocks of companies with:
*  A strong business franchise that offers growth potential.
*  Products and services that give them a competitive advantage.
*  A stock price its advisor believes reasonable relative to the assets and
   earning power of the company. 

Acorn Fund is a global fund. It invests the majority of its assets in U.S.
companies, but also invests a portion of its holdings in companies outside of
the U.S.

You may want to invest if you:
*  Are seeking to complement your existing equity holdings with a global growth
   fund.
*  Are seeking a stock fund that emphasizes the less-profiled stocks of small-
   to medium-sized companies.
*  Are seeking growth of your capital over the long-term (at least 5 years.)

You may not want to invest if you:
*  Are seeking a significant amount of current dividend income.
*  Are unwilling to accept short-term fluctuations in share price.
*  Have short-term investment goals or needs.

Risks of Investing in Acorn Fund

Smaller company stocks are often more volatile or less liquid than the stocks of
larger companies.

You could lose money on your investment in the fund, or the fund could
underperform other investments, if any of the following occurs:
*  The stock market goes down.
*  Small- to mid-cap stocks trail returns of the overall market.
*  The stocks selected for the portfolio do not perform as expected.

Investments in foreign securities may have special risks in addition to those
mentioned above, including:
*  Political or economic instability
*  Higher transaction costs
*  Currency exchange rate fluctuations

2
<PAGE>
 
Acorn Fund
Performance


The following chart and table illustrate annual fund returns for each of the
past 10 years as well as a comparison of returns of Acorn Fund, the S&P 500 and
the Russell 2000 for the 1-, 5- and 10-year periods ended 12/31/1998.

This information is intended to help you assess the variability of fund returns
over the past 10 years (and consequently the potential risks of fund
investment).

Total Return
[Bar Graph here]

Total Return        Year
  25%               1989
 (18%)              1990
  47%               1991
  24%               1992
  32%               1993
  (7%)              1994
  21%               1995
  23%               1996
  25%               1997
   6%               1998

<TABLE>
<CAPTION>


Acorn Fund's highest and lowest quarterly returns for the 10 years ended 12/31/1998 were

                                              quarters ended
- ------------------------------------------------------------
<S>                                <C>            <C>
highest                            19.3%          3/31/91
lowest                            -23.8%          9/30/90
</TABLE>

The fund's past performance is not an indication of future performance.
<TABLE>
<CAPTION> 
Average Annual Total Returns for Periods ended 12/31/1998
                                  1 Year   5 Years   10 Years
- -------------------------------------------------------------
<S>                               <C>      <C>       <C>  
Acorn Fund                         6.0%     12.7%     16.3%
S&P 500*                          28.6%     24.1%     19.2%
Russell 2000*                     -2.6%     11.9%     12.9%
</TABLE>

Acorn Fund's holdings are not identical to the S&P 500, the Russell 2000 or any
other market index. Therefore, the performance of the fund will not mirror the
returns of any particular index.

*The S&P 500 Index is a broad market-weighted average of U.S. blue-chip
 companies. The Russell 2000 Index is an unmanaged, market-weighted index, with
 dividends reinvested, of 2,000 small companies, formed by taking the largest
 3,000 small companies and eliminating the largest 1,000 of those companies.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the fund.

Shareholder Transaction Expenses
Fees paid directly from your investment:
<TABLE> 
<CAPTION> 
<S>                        <C> 
Maximum sales charge        None
Deferred sales charge       None
Exchange fee                None
Redemption fee              None
</TABLE> 

<TABLE> 
<CAPTION> 
Annual Fund Operating Expenses
Expenses that are deducted from fund assets:
<S>                        <C> 
Management fees             .69%
12b-1 fee                   None
Other expenses              .15%
                            ----
Total annual fund
operating expenses          .84%
</TABLE> 

Example

This example is intended to help you compare the cost of investing in the fund
with the costs of investing in other mutual funds. It assumes you invest $10,000
in the fund for the time period indicated ending on December 31, 1998, earn a
5% return each year, reinvest all of your dividends and distributions, and that
operating expenses remain constant. Your actual costs may be higher or lower.

<TABLE> 
<CAPTION> 
<S>                 <C>
1 Year              $   86
3 Years             $  268
5 Years             $  466
10 Years            $1,037
</TABLE>

                                                                               3
<PAGE>
 
AT A GLANCE      Acorn International 


Fund Objective

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


Investment Strategy

Acorn International is a diversified mutual fund that invests primarily in
stocks of non-U.S. small- and medium-size companies. The fund generally invests
in the stocks of companies based outside of the U.S. (or whose primary business
takes place outside of the U.S.) with capitalizations of less than $1 billion
with the intention of holding them as they grow and selling them when they
become large.

The fund believes that these smaller, less profiled companies--particularly
outside of the U.S.-- may offer higher return potential than the stocks of large
companies.

Acorn International typically looks for the stocks of companies with:
*  A strong business franchise that offers growth potential.
*  Products and services that give them a competitive advantage.
*  A stock price its advisor believes reasonable relative to the assets and
   earning power of the company.

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 outside the U.S.

You may want to invest if you:
*  Are seeking to diversify your existing equity holdings with a fund that
   invests in the stocks of companies outside the U.S.
*  Are seeking a stock fund that emphasizes the less-profiled stocks of 
   small- to medium-sized companies.
*  Are seeking growth of your capital over the long-term (at least 5 years.)

You may not want to invest if you:
*  Are seeking a significant amount of current dividend income.
*  Are unwilling to accept short-term fluctuations in share price.
*  Have short-term investment goals or needs.

Risks of Investing in Acorn International

Smaller company stocks are often more volatile or less liquid than the stocks of
larger companies.

You could lose money on your investment in the fund, or the fund could
underperform other investments, if any of the following occurs:
*  International stock markets go down.
*  Foreign small- to mid-cap stocks trail returns of the overall market.
*  The stocks selected for the portfolio do not perform as expected.

Investments in foreign securities may have special risks in addition to those
mentioned above, including:
*  Political or economic instability
*  Higher transaction costs
*  Currency exchange rate fluctuations

4
<PAGE>
 
Acorn International
Performance


The following chart and table illustrate annual fund returns for the past 6
years as well as a comparison of returns of Acorn International, the EAFE and
EMI for the periods listed.

This information is intended to help you assess the variability of fund returns
over the past 6 years (and consequently the potential risks of fund investment).

Total Return
[Bar Graph appears here]

  Year       Return
  1993         49%
  1994         (4%)
  1995          9%
  1996         21%
  1997         .2%
  1998         15%


Acorn International's highest and lowest quarterly returns for the 6 years ended
12/31/1998 were
<TABLE>
<CAPTION>

                                                quarters ended
- --------------------------------------------------------------
<S>                              <C>              <C>   
highest                           18.2%            3/31/98
lowest                           -16.1%            9/30/98
</TABLE>

The fund's past performance is not an indication of future performance.

Average Annual Total Returns for Periods ended 12/31/1998
<TABLE>
<CAPTION>

                               1 Year    5 Years    since inception*
- --------------------------------------------------------------------
<S>                           <C>        <C>            <C> 
Acorn Int'l                    15.4%      7.9%           14.5%
EAFE+                          20.0%      9.2%           11.5%
EMI (world ex-U.S.)+           12.2%      4.5%            7.4%
</TABLE>


Acorn International's holdings are not identical to the EAFE, the EMI or any
other market index. Therefore, the performance of the fund will not mirror the
returns of any particular index.

*Acorn International's inception 9/23/1992. Beginning date for EAFE is
 9/30/1992.
+Morgan Stanley's Europe, Australasia and Far East Index (EAFE) is an unmanaged
 index of companies throughout the world in proportion to world stock market
 capitalizations, excluding the U.S. and Canada. EMI (world ex-U.S.) is Salomon
 Brothers' index of the bottom 20% of institutionally investable capital of
 countries, selected by Salomon and excluding the U.S.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the fund.

Shareholder Transaction Expenses
Fees paid directly from your investment:
<TABLE> 
<CAPTION> 
<S>                       <C> 
Maximum sales charge       None
Deferred sales charge      None
Exchange fee               None
Redemption fee             None
</TABLE> 


Annual Fund Operating Expenses
Expenses that are deducted from fund assets:
<TABLE> 
<CAPTION> 
<S>                       <C> 
Management fees            .82%
12b-1 fee                  None
Other expenses             .30%
                           ----
Total annual fund
operating expenses        1.12%
</TABLE> 

Example

This example is intended to help you compare the cost of investing in the fund
with the costs of investing in other mutual funds. It assumes you invest $10,000
in the fund for the time period indicated ending on December 31, 1998, earn a
5% return each year, reinvest all of your dividends and distributions, and that
operating expenses remain constant. Your actual costs may be higher or lower.

<TABLE> 
<CAPTION> 
<S>                 <C>
1 Year              $  114
3 Years             $  356
5 Years             $  617
10 Years            $1,363
</TABLE>

                                                                               5
<PAGE>
 
AT A GLANCE       Acorn USA 


Fund Objective

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

Investment Strategy

Acorn USA is a diversified mutual fund that invests primarily in stocks of 
small- and medium-size U.S. companies. The fund generally invests in the stocks
of U.S. companies with capitalizations of less than $1 billion with the
intention of holding them as they grow and selling them when they become large.

The fund believes that these smaller, less profiled companies may offer higher
return potential than the stocks of large companies.

Acorn USA typically looks for the stocks of companies with:
*  A strong business franchise that offers growth potential.
*  Products and services that give them a competitive advantage.
*  A stock price its advisor believes reasonable relative to the assets and
   earning power of the company.

You may want to invest if you:
*  Are seeking to complement your existing domestic equity holdings with a
   smaller company growth fund.
*  Are seeking a stock fund that emphasizes the less-profiled stocks of small-
   to medium-sized companies.
*  Are seeking growth of your capital over the long-term (at least 5 years.)

You may not want to invest if you:
*  Are seeking a significant amount of current dividend income.
*  Are unwilling to accept short-term fluctuations in share price.
*  Have short-term investment goals or needs.

Risks of Investing in Acorn USA

Smaller company stocks are often more volatile or less liquid than the stocks of
larger companies.

You could lose money on your investment in the fund, or the fund could
underperform other investments, if any of the following occurs:
*  The stock market goes down.
*  Small- to mid-cap stocks trail returns of the overall market.
*  The stocks selected for the portfolio do not perform as expected.

6
<PAGE>
 
Acorn USA
Performance

The following chart and table illustrate annual fund returns for the past 2
years as well as a comparison of returns of Acorn USA and the Russell 2000 for
the periods listed.

This information is intended to help you assess the variability of fund returns
over the past 2 years (and consequently the potential risks of fund investment).

Total Return
[Bar Graph appears here]
  Year   Return
  1997     32%
  1998      6%


 
Acorn USA's highest and lowest quarterly returns for the 2 years ended
 12/31/1998 were
<TABLE>
<CAPTION>

                                         quarters ended
- -------------------------------------------------------
<S>                         <C>             <C>
highest                      16.0%           6/30/97
lowest                      -19.25%          9/30/98
</TABLE>
The fund's past performance is not an indication of future performance.

Average Annual Total Returns for Periods ended 12/31/1998
<TABLE>
<CAPTION>
                                          1 Year   since inception*
- -------------------------------------------------------------------
<S>                                       <C>          <C>
Acorn Fund                                 5.8%         23.5%
Russell 2000 +                            -2.6%         12.0%
</TABLE>
Acorn USA's holdings are not identical to the Russell 2000 or any other market
index. Therefore, the performance of the fund will not mirror the returns of any
particular index.

*Acorn USA's inception on 9/4/1996.

+The Russell 2000 Index is an unmanaged, market-weighted index, with dividends
 reinvested, of 2,000 small companies, formed by taking the largest 3,000 small
 companies and eliminating the largest 1,000 of those companies.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the fund.

Shareholder Transaction Expenses
Fees paid directly from your investment:
<TABLE> 
<CAPTION> 
<S>                         <C> 
Maximum sales charge         None
Deferred sales charge        None
Exchange fee                 None
Redemption fee               None
</TABLE> 

Annual Fund Operating Expenses
Expenses that are deducted from fund assets:
<TABLE> 
<CAPTION> 
<S>                          <C> 
Management fees              .94%
12b-1 fee                    None
Other expenses               .26%
                            -----
Total annual fund
operating expenses          1.20%
</TABLE> 

Example

This example is intended to help you compare the cost of investing in the fund
with the costs of investing in other mutual funds. It assumes you invest $10,000
in the fund for the time period indicated ending on December 31, 1998, earn a 5%
return each year, reinvest all of your dividends and distributions, and that
operating expenses remain constant. Your actual costs may be higher or lower.

<TABLE> 
<CAPTION> 
<S>                 <C>
1 Year              $  122
3 Years             $  381
5 Years             $  660
10 Years            $1,455
</TABLE>

                                                                               7
<PAGE>
 
AT A GLANCE        Acorn Twenty 


Fund Objective

Acorn Twenty seeks long-term growth of capital.


Investment Strategy

Acorn Twenty invests primarily in the stocks of medium- to larger-size 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 $1 billion to $10
billion, offering the potential to provide above average growth over time.

The fund believes that companies within this capitalization range are less
profiled, and may offer higher return potential, than the stocks of companies
with capitalizations above $10 billion.

Acorn Twenty typically looks for the stocks of companies with:
*  A strong business franchise that offers growth potential.
*  Products and services that give them a competitive advantage.
*  A stock price its advisor believes reasonable relative to the assets and
   earning power of the company.

You may want to invest if you:
*  Are seeking to complement your existing domestic equity holdings with a
   focused stock fund.
*  Are seeking a stock fund that emphasizes the less profiled stocks of medium-
   to-larger sized companies.
*  Are seeking growth of your capital over the long-term (at least 5 years.)

You may not want to invest if you:
*  Are seeking a significant amount of current dividend income.
*  Are unwilling to accept short-term fluctuations in share price or the more
   volatile returns of a non-diversified fund.
*  Have short-term investment goals or needs.

Risks of Investing in Acorn Twenty

Acorn Twenty is a non-diversified fund. Therefore, each stock may represent a
significant part of its overall portfolio. The performance of each of these
larger holdings will have a greater impact on the fund's total return, and may
make the fund's returns more volatile than a more diversified fund.

Mid-cap stocks are more volatile and may be less liquid than large-cap stocks.
Mid-cap companies may have a shorter history of operations and a smaller market
for their shares. You could lose money on your investment in the fund, or the
fund could underperform other investments, if any of the following occurs:
*  The stock market goes down.
*  Mid-cap stocks trail returns of the overall market.
*  The stocks selected for the portfolio do not perform as expected.

8
<PAGE>
 
Acorn Twenty Performance

Total Return and Average Annual Total Return information is not available for
Acorn Twenty because the fund has been in operation less than one full calendar
year.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the fund.

Shareholder Transaction Expenses
Fees paid directly from your investment:
<TABLE> 
<CAPTION> 
<S>                         <C> 
Maximum sales charge         None
Deferred sales charge        None
Exchange fee                 None
Redemption fee               None
</TABLE> 

Annual Fund Operating Expenses
Expenses that are deducted from fund assets:
<TABLE> 
<CAPTION> 
<S>                         <C> 
Management fees              .90%
12b-1 fee                    None
Other expenses               .93%
                            -----
Total annual fund
operating expenses*         1.83%
</TABLE> 

*Wanger Asset Management has undertaken to limit Acorn Twenty's annual expenses
 to 1.35% of its average net assets. This expense limitation undertaking is
 voluntary and is terminable by either the fund or WAM on 30 days' notice to the
 other. For the period from commencement of operations on November 23, 1998
 through December 31, 1998, the reduction in the fund's expenses was represented
 by an advisory fee reimbursement of .42% of the fund's average daily net assets
 and an earnings credit for cash balances maintained with the custodian of .06%
 of the fund's daily net assets.

Example

This example is intended to help you compare the cost of investing in the fund
with the costs of investing in other mutual funds. It assumes you invest $10,000
in the fund for the time period indicated ending on December 31, 1998, earn a
5% return each year, reinvest all of your dividends and distributions, and that
operating expenses remain constant. Your actual returns and costs may be higher
or lower.

1 Year        $186
3 Years       $576

                                                                               9
<PAGE>

AT A GLANCE        Acorn Foreign Forty 


Fund Objective

Acorn Foreign Forty seeks long-term growth of capital.

Investment Strategy

Acorn Foreign Forty invests primarily in the stocks of medium- to larger-size
companies based in developed markets 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 $1
billion to $10 billion, offering the potential to provide above average growth
over time.

The fund believes that companies within this capitalization range are less
profiled, and may offer higher return potential, than the stocks of companies
with capitalizations above $10 billion.

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

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.

   You may want to invest if you:
*  Are seeking to complement your existing equity holdings with an international
   stock fund.
*  Are seeking a stock fund that emphasizes the less-profiled stocks of medium-
   to-larger sized companies.
*  Are seeking growth of your capital over the long-term (at least 5 years.)

   You may not want to invest if you:
*  Are seeking a significant amount of current dividend income.
*  Are unwilling to accept short-term fluctuations in share price or the more
   volatile returns of a non-diversified fund.
*  Have short-term investment goals or needs.

Risks of Investing in Acorn Foreign Forty

Acorn Foreign Forty is a non-diversified fund that ordinarily holds 40 to 60
stocks. The fund takes larger positions in some of its stocks than others. The
performance of each of these larger holdings will have a greater impact on the
fund's total returns, and may make the fund's returns more volatile than a more
diversified international fund.

Mid-cap stocks are more volatile and may be less liquid than large-cap stocks.
Mid-cap companies may have a shorter history of operations and a smaller market
for their shares.
 
   You could lose money on your investment in the fund, or the fund could
   underperform other investments, if any of the following occurs:
*  International stock markets go down.
*  Foreign mid- to large-cap stocks trail returns of the overall market.
*  The stocks selected for the portfolio do not perform as expected.

   Investments in foreign securities may have special risks in addition to those
   mentioned above, including:
*  Political or economic instability.
*  Higher transaction costs.
*  Currency exchange rate fluctuations.

10
<PAGE>
 
Acorn Foreign Forty
Performance

Total Return and Average Annual Total Return information is not available for
Acorn Foreign Forty because the fund has been in operation less than one full
calendar year.

Fees and Expenses

This table describes the fees and expenses that you may pay if you buy and hold
shares of the fund.

Shareholder Transaction Expenses
Fees paid directly from your investment:
<TABLE> 
<CAPTION> 
<S>                         <C> 
Maximum sales charge          None
Deferred sales charge         None
Exchange fee                  None
Redemption fee                None
</TABLE> 

Annual Fund Operating Expenses
Expenses that are deducted from fund assets:
<TABLE> 
<CAPTION> 
<S>                         <C> 
Management fees              .95%
12b-1 fee                    None
Other expenses              1.75%
                            -----
Total annual fund
operating expenses*         2.70%
</TABLE> 

*Wanger Asset Management has undertaken to limit Acorn Foreign Forty's annual
 expenses to 1.45% of its average net assets. This expense limitation
 undertaking is voluntary and is terminable by either the fund or WAM on 30
 days' notice to the other. For the period from commencement of operations on
 November 23, 1998, through December 31, 1998, the reduction in the fund's
 expenses was represented by an advisory fee reimbursement of .97% of the fund's
 average daily net assets and an earnings credit for cash balances maintained
 with the custodian of .28% of the fund's daily net assets.

Example

This example is intended to help you compare the cost of investing in the fund
with the costs of investing in other mutual funds. It assumes you invest $10,000
in the fund for the time period indicated ending on December 31, 1998, earn a
5% return each year, reinvest all of your dividends and distributions, and that
operating expenses remain constant. Your actual returns and costs may be higher
or lower.

1 Year        $273
3 Years       $838

                                                                              11
<PAGE>
 
Management of the Funds

                    The Acorn Family of Funds is managed by Wanger Asset
                    Management, L.P. (WAM), 227 West Monroe Street, Suite 3000,
                    Chicago, Illinois 60606. WAM chooses the funds' investments
                    and handles their business affairs under the direction of
                    the board of trustees. WAM is a limited partnership managed
                    by its general partner, Wanger Asset Management, Ltd. WAM
                    manages over $6.4 billion in assets.

                    WAM uses a team approach when managing the funds. The
                    management teams consist of a lead portfolio manager (or co-
                    managers), other WAM portfolio managers, and research
                    analysts. 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 lead portfolio manager and co-managers are
                    responsible for making daily portfolio selection decisions,
                    and utilize the management team's input and advice when
                    making buy and sell determinations.

Portfolio Managers  Ralph Wanger
                    Lead portfolio manager, Acorn Fund
                    Ralph Wanger is chief strategist of the Acorn Family of
                    Funds and has been involved in managing all of the funds and
                    developing their investment strategies since each fund
                    began. He has been president and a member of the board of
                    trustees of Acorn Investment Trust (Acorn) since 1970, and
                    is a principal of WAM. 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, Acorn Fund
                    Charles P. MCQuaid is a senior vice president and member of
                    Acorn's board of trustees, and is the director of research
                    and a principal of WAM. Mr. MCQuaid went to work for Acorn
                    in 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
                    Lead portfolio manager, Acorn International
                    Leah Zell is a vice president of Acorn, and a principal of
                    WAM. She has managed Acorn International since its inception
                    in 1992, and was named lead portfolio manager in 1997. She
                    has also worked with 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 from 
                    Radcliffe and PHd from Harvard University.


                    Margaret M. Forster
                    Co-portfolio manager, Acorn International
                    Margaret Forster is a vice president of Acorn and became co-
                    portfolio manager of Acorn International in May, 1999. She
                    has been a key member of the international analytical team
                    since 1994 and a principal of WAM since January, 1999.
                    Before joining WAM, 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 BA from Universidade de Sao
                    Paulo, Escola Politecnica, and an MBA, MS and PHd from
                    Cornell University.


                    Robert A. Mohn
                    Lead portfolio manager, Acorn USA
                    Robert Mohn is a vice president of Acorn. He has been a key
                    member of WAM'S domestic analytical team since 1992, and a
                    principal of WAM since 1995. He has managed Acorn USA since
                    its inception in 1996, and also manages a mutual fund

12
<PAGE>

- --------------------------------------------------------------------------------
                    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.


                    Marcel P. Houtzager
                    Lead portfolio manager, Acorn Foreign Forty
                    Marcel Houtzager is a vice president of Acorn, and has
                    managed Acorn Foreign Forty since its inception in 1998. He
                    has been a key member of WAM's international analytical team
                    since 1992, and a principal of WAM since 1995. 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.


                    John H. Park
                    Co-portfolio manager, Acorn Twenty
                    John Park is a vice president of Acorn, and has co-managed
                    Acorn Twenty since its inception in 1998. He has been a key
                    member of WAM's domestic investment team since 1993, and a
                    principal of WAM since 1998. Mr. Park is also co-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.


                    Mark H. Yost
                    Co-portfolio manager, Acorn Twenty 
                    Mark Yost is a vice president of Acorn, and has co-managed
                    Acorn Twenty since its inception in 1998. He has been a key
                    member of WAM's domestic investment team since 1995. Before
                    joining WAM, Mr. Yost was an investment analyst for First
                    Chicago Corporation. Mr. Yost also manages the WAM Yost
                    Partnership, L.P., a smaller company focused limited
                    partnership, is co-manager of a mutual fund underlying
                    variable insurance products and manages the portfolio of an
                    investment company whose shares are offered only to non-U.S.
                    investors. He is a CFA and earned his BA from St. Olaf
                    College and his MBA from the University of Chicago.

- --------------------------------------------------------------------------------
Management Fees     WAM earns the following advisory fees for managing the Acorn
                    Family of Funds:
                    -----------------------------------------------
                    Fund Name               Fund Fee as a % of
                                            Average Net Assets
                                            (12/31/98)
                    -----------------------------------------------
                    Acorn Fund              .69%
                    Acorn International     .82%
                    Acorn USA               .94%
                    Acorn Twenty            .90%
                    Acorn Foreign Forty     .95%



                    WAM also receives an administrative services fee from each
                    fund equal to .05% of that fund's average annual net assets.

                                                                              13
<PAGE>
 
How the Funds Invest


The Acorn
Investment
Philosophy


The Information Edge

WAM has built a reputation on innovative thinking and unconventional stock
picks. We rely primarily on our independent, internally-generated research to
uncover companies that may be less profiled than the more popular names. This is
where WAM adds the greatest value to Acorn shareholders.

WAM's research process is constantly uncovering quality companies that exhibit
exciting characteristics-- companies that rest on a solid tripod of growth
potential, financial strength and fundamental value.


Growth Potential

 . superior technology
 . innovative marketing
 . solid management
 . strategic or niche position
 . superior earnings prospects
 . fast growing economy

The realization of this growth potential would likely produce superior
performance that is sustainable over time.

Financial Strength

 . stability
 . reduced risk
 . competitive advantage

A strong balance sheet gives management greater flexibility to pursue strategic
objectives and is essential to maintaining a competitive advantage.

Fundamental Value

 . lower stock price relative to growth potential and capitalization
 . growth at a reasonable price

Once we uncover a great company, we identify a price that we believe would also
make the stock a good value.

Stock Strength Comes First

WAM primarily follows a bottom-up approach to portfolio construction, placing
greater emphasis on the merits of each individual stock.

Our analysts continually screen companies, including making over 1,000 face-to-
face visits around the globe each year. We want to know everything we can about
each Acorn investment to avoid surprises. To accomplish this, our analysts talk
directly to top management whenever possible.

Sometimes, WAM's analysts will use a top-down investment approach to
generate ideas for new investments. This approach is broader in scope than a
bottom-up approach. Here, the analytical teams identify current investment
themes, or trends, and set regional and industry allocations.

We believe that our thorough research helps us maintain lower taxes and
transaction costs. In managing the funds, we try to reduce these costs by
investing with a long-term time horizon (at least 2-5 years). Occasionally,
however, securities purchased on a long-term basis may be sold within 12 months
after purchase in light of a change in the circumstances of a particular company
or industry, or in general market or economic conditions.

                                       14
<PAGE>
 
Securities in Which the Funds Invest and Risks

Common Stocks

The Acorn funds invest mostly in common stocks. Common Stocks represent an
equity (ownership) interest in a corporation.

Acorn Fund, Acorn International and Acorn USA invest mainly in the common stocks
of small and medium-sized companies, with market capitalizations of less than $1
billion. Acorn Twenty and Acorn Foreign Forty invest mostly in the stocks of
companies with market capitalizations of $1-$10 billion.

Foreign Securities

Acorn International and Acorn Foreign Forty invest most of their assets in non-
U.S. securities. Acorn Fund has significant foreign investments, although most
of its assets are invested in the U.S. Acorn USA and Acorn Twenty invest most of
their assets in the U.S., and only intend to invest a part of their assets
overseas under certain circumstances (see Portfolio Allocation below).

Portfolio Allocation

Under normal conditions, the funds' common stock investments (as a percentage of
total assets) are limited by the following maximum allocations:

<TABLE>
<CAPTION>
 
                         % in U.S. companies   % in non-U.S. companies
<S>                      <C>                   <C>
Acorn Fund                          no limit                  up to 33%
- -----------------------------------------------------------------------
Acorn International                 up to 25%                  no limit
- -----------------------------------------------------------------------
Acorn USA                           no limit                  up to 10%
- -----------------------------------------------------------------------
Acorn Twenty*                       no limit                  up to 15%
- -----------------------------------------------------------------------
Acorn Foreign Forty**               up to 15%                  no limit

</TABLE>

* Acorn Twenty will normally invest in a non-U.S company, only if operations are
  located within the U.S.
**Acorn Foreign Forty will normally invest in a U.S. company, only if operations
  are primarily located outside of the U.S.

  Acorn's board of trustees may change each fund's investment objective without 
shareholder approval.

Throughout this prospectus we've identified the areas that contain specific 
information about risk with [Acorn symbol here].  Please read to fully 
understand your investment.

Summarizing Risk

When you invest in a mutual fund, you are exposed to certain risks. These
include the risk that you may receive little or no return on your investment, or
that you may even lose part or all of your investment. Investments that provide
higher potential reward also present greater risk. Likewise, investments with
lower potential reward have lower risk. Before investing in one of the Acorn
funds, you should carefully consider the risks associated with that particular
fund. Because of these risks, you should consider an investment in any of the
Acorn funds a long-term investment.

                                                                              15
<PAGE>
 
How the Funds Invest continued


Common Stocks

Over time, common stocks have historically provided superior long-term capital
growth potential. However, stock prices may decline over short or even extended
periods. Stock markets tend to move in cycles, with periods of rising stock
prices and periods of falling stock prices. As a result, the funds should be
considered long-term investments, designed to provide the best results when held
for several years or more.


Small and Medium Companies

Acorn prefers small and medium companies over the stocks of large companies.
During some periods, the securities of smaller companies and the stocks of
medium companies, as a class, have performed better than the securities of
larger companies, and in some periods they have performed worse. Securities of
smaller companies may be more volatile and less liquid than the stocks of large
companies.


Foreign Securities

International investing allows you to achieve greater diversification and to
take advantage of changes in foreign economies and market conditions. From time
to time, many foreign economies have grown faster than the U.S. economy, and the
returns on investments in these countries have exceeded those of similar U.S.
investments, although there can be no assurance that these conditions will
continue.

Investments in foreign securities provide opportunities different from those
available in the U.S., and risks that in some ways may be greater than in U.S.
investments. These risks may have a negative effect on the fund's NAV and
include fluctuations in exchange rates of foreign currencies; less public
information with respect to issuers of securities; less governmental supervision
of stock exchanges, securities brokers and issuers of securities; different
accounting, auditing and financial reporting standards; different settlement
periods and trading practices; less liquidity, frequently greater price
volatility and higher transactions costs and the possible imposition of foreign
taxes. Investing in countries outside the U.S. may also involve political risk.
Economies in individual markets may differ favorably or unfavorably from the
U.S. economy in such respects as gross domestic product, rates of inflation,
debt structure and currency valuation.

Securities markets in emerging countries may be substantially smaller, less
developed, less liquid, and more volatile than the securities markets of the
U.S. and other developed countries.


16

<PAGE>
 
Managing Risk

WAM uses various techniques and practices to mitigate the funds' exposure to
risk.


Investment Limitations

Each fund has adopted the following investment limitations (generally based upon
a percentage of total assets) that cannot be changed without shareholder
approval and are designed to limit risk:

 .  None of the funds may invest more than 5% in securities of any one issuer,
   except for U.S. government securities.*

 .  None of the funds may invest more than 25% in any one issuer or more than 25%
   in any one industry (in each case with the exception of U.S. government
   securities).

*This restriction applies to only 75% of the total assets of each of Acorn
 International and Acorn USA, and to only 50% of the total assets of each of
 Acorn Twenty and Acorn Foreign Forty.


Defensive Investment Strategies

The funds' portfolio managers may use the following strategies if they believe
that a temporary defensive position is advisable. With respect to Acorn
International and Acorn Foreign Forty, this includes times when investment in
foreign securities appears to be relatively unattractive because of current or
anticipated adverse political or economic conditions.

 .  Each fund may invest without limit in U.S. corporate and government
   obligations.
 
 .  Each fund may hold cash or cash equivalents.

 .  Each fund may hold cash in domestic and foreign currencies and may invest in
   domestic and foreign money market securities to meet liquidity needs.
   (Generally, this is not expected to exceed 25% of total assets.)

During these periods, a fund's assets may not be invested in accordance with its
strategy, and the fund may not achieve its investment objective.


Hedging Strategies

Each fund may hedge against variations in exchange rates, or to protect against
exposure in the equity markets. Portfolio managers try to accomplish this by
buying and selling:

 .  options,
 .  futures contracts,
 .  options on futures contracts,
 .  currency exchange contracts,
 .  swap agreements, or
 .  put and call options.

If a fund is not successful when using these techniques, total return could be
adversely affected.


Year 2000

Some of today's computer systems cannot process date-related information because
they are not programmed to distinguish between the year 2000 and the year 1900
(commonly referred to as the Year 2000 or Y2K problem). WAM is working closely
with the funds' service providers to ensure the proper functioning of the
computer systems on which the funds depend for smooth operation. Based on the
information currently available, WAM does not anticipate any material impact on
the delivery of services currently provided. There can be no assurance, however,
that the steps taken by WAM in preparation for the year 2000 will be sufficient
to avoid any adverse impact on the funds.

In addition, Year 2000 issues can have a negative impact on the business results
and prospects of issuers of securities held by a fund. Although WAM considers
the status of the issuer's preparations for the year 2000, it has not had a
material effect on the decision to buy or sell securities thus far.


                                                                              17

<PAGE>
 
Your Account

- --------------------------------------------------------------------------------
Doing Business
With Acorn

Acorn shareholder service representatives are available Monday through Friday
(except holidays) from 8:00 a.m. to 4:30 p.m. Central time. Call one of the 
toll-free numbers in the table below to reach the appropriate representative.

- --------------------------------------------------------------------------------
Toll-free number                        Reason for call
- --------------------------------------------------------------------------------
Fund Advisor (WAM):
1-800-9-ACORN-9 (1-800-922-6769)      . For general fund information
                                      . For prices
outside the U.S. call 1-312-634-9240  . For Acorn literature and account forms
 
Transfer Agent:
1-800-962-1585                        . To buy, sell, or exchange shares
                                      . To change your address
outside the U.S.                      . To establish an account by phone 
call 1-617-328-5000, ext. 55462         (existing shareholders only)
                                      . For any other account maintenance or
                                        transactions 
                                      . For IRA assistance
                                      . For 24-hour account balances

Transfer Agent/TDD Service
1-800-306-4567                        . TDD service for the deaf and hearing 
                                        impaired

Web Site:
www.acornfunds.com                    . For daily and historical prices
                                      . For general fund information
                                      . For fund literature
                                      . To e-mail the Acorn funds
                                      . For distribution estimates

18
<PAGE>
  
- --------------------------------------------------------------------------------
                       Investment Minimums
                       ------------------------------
                       To open an account      $1,000
                       ------------------------------
                       To open an IRA          $1,000
                       ------------------------------
                       To add to an account    $  100
- --------------------------------------------------------------------------------
Choices for Your       Open a New Acorn Account
Account Registration   To invest with Acorn you must be a U.S. resident
                       with a social security or tax identification number.
                       You can open a new account in any of the following
                       ways:
                       
                       Mail us a completed account application and a check
                       or money order payable to Fund Name for $1,000 or
                       more.
                       
                       Regular mail            Overnight mail
                       State Street Bank       Boston Financial Data Services
                        and Trust Company      Attn: Acorn Family of Funds
                       Attn: Acorn Family of   66 Brooks Drive             
                        Funds                  Braintree, MA  02184
                       PO Box 8502             1-617-328-5000 ext. 55462 or
                       Boston, MA 02266-8502    1-800-962-1585                 
                                         
                                                                               
                       Current Acorn shareholders may also open a new,
                       identically registered Acorn account by:
                       
                     . using the telephone exchange plan to switch $1,000 or
                       more from your existing Acorn account (or from a money
                       fund offered through the exchange plan) into a new Acorn
                       account.

                     . wire by simply calling 1-800-962-1585 to arrange for 
                       this transaction. (Not Available for IRA accounts.)
                       ---------------------------------------------------------
                       Add to an Existing Acorn Account
                       You may add to your existing Acorn account in any of the 
                       following ways:

                       Mail a check or money order payable to Fund Name for $100
                       or more to either address above. You may send your check
                       by itself (make sure to identify your Acorn account
                       number on the check), or you may include a stub from an
                       Acorn account statement.

                       Use the telephone exchange plan to switch money from one
                       Acorn account to another (or from one of the money funds
                       offered through the exchange plan).

                                                                             19
<PAGE>
 
Your Account continued

- -------------------------------------------------------------------------------
Wire money from your bank account using the following wire instructions:

State Street Bank & Trust Company
Attn: Mutual Funds
Boston, MA 02110
Routing #0110-0002-8
Deposit DDA #9902-990-2
(specify the fund name and account number)

Use the telephone purchase plan to move money from your bank account to your
Acorn account via ACH transfer. To use the telephone purchase plan, you must
select this feature on your account application or add this by completing a
Doing Business With Acorn form. Note: The price you receive for your purchased
shares will be the NAV calculated at Closing Time the next business day (see
Shareholder and Account Policies--Share Price).

Use the automatic investment plan to move money from your bank account to your
Acorn account via ACH transfer. You may establish this on a monthly or quarterly
basis for $100 to $50,000 per period. Quarterly investments occur in January,
April, July and October. The money will be transferred on or about the 15th of
the month unless you designate a different day (must be after the 4th of the
month). if the day you select falls on a Saturday, Sunday, holiday or any other
day when the New York Stock Exchange (NYSE) is closed for trading, Acorn will
process the transaction on the next business day. You may change your automatic
investment amount or frequency by calling 1-800-962-1585 at least one week prior
to your next scheduled investment date.

- -------------------------------------------------------------------------------
How to Buy Shares

General Policies for Buying Acorn Shares

The following policies apply any time you buy shares of the Acorn funds.

 . All purchases must be made in U.S. dollars and checks must be drawn on U.S.
  banks. The Acorn funds do not accept third party checks, except for properly
  endorsed IRA rollover checks.

 . Acorn does not accept cash, credit cards, or credit card checks.

 . If payment for your check or telephone purchase order does not clear, Acorn
  will cancel your purchase and you will be liable for any losses or fees the
  fund or its transfer agent incurs.

 . Your participation in the automatic investment plan and telephone purchase
  plan may be immediately terminated if any item is unpaid by your financial
  institution.

The Acorn funds do not permit market-timing and have adopted policies to
discourage this practice.

Each fund reserves the right to reject any specific request to buy shares,
including certain purchases through the telephone exchange plan (see Exchange
Plan Restrictions). Acorn may refuse a purchase if it could disrupt management
of the fund or would not be in the best interests of the fund's existing
shareholders.

20
<PAGE>
<TABLE> 
<CAPTION> 

How to Sell Shares     You may sell your Acorn shares in several different ways.

                       Mail us a letter of instruction that includes:
                      <S>                                     <C>  
                     . your name;
                     . the fund name and account number;
                     . the dollar amount or number of shares you want to sell; and
                     . any unsigned stock certificates representing the shares
                       you want to sell (if applicable) to:

                       Regular mail                            Overnight mail
                       State Street Bank and Trust Company     Boston Financial Data Services
                       Attn: Acorn Family of Funds             Attn: Acorn Family of Funds
                       PO Box 8502                             66 Brooks Drive
                       Boston, MA 02266-8502                   Braintree, MA 02184
                                                               1-617-328-5000 ext. 55462 or 1-800-962-1585

                       Sell your shares by telephone using the telephone redemption plan. The plan lets
                       you sell $100 to $50,000 per day by phone. (You are eligible for the telephone
                       redemption plan service, unless you declined it on your account application.)

                       Note: For your protection, you may not sell shares by telephone or by letter of instruction without a
                       signature guarantee if you have changed your account's address within the past 60 days. Shares must be
                       redeemed with a letter of instruction (as described above), with all registered account owners' signatures
                       guaranteed.

                       Establish the systematic withdrawal plan on your account. This plan allows you
                       to redeem a specified dollar amount of shares from your account on a monthly or
                       quarterly basis. You must have an account balance of at least $25,000 to be
                       eligible for this service.
</TABLE> 

                       General Policies for Selling Acorn Shares

                       The following policies apply any time you sell shares of
                       any of the Acorn funds.

                     . Normally, Acorn will mail your redemption
                       proceeds within seven days after receiving
                       your redemption request.

                     . Redemption checks are made payable to the shareholder(s)
                       of record, unless otherwise requested in writing with all
                       registered account owners' signatures guaranteed.

                     . Redemptions on recent purchases made by check, automatic
                       investment plan, or telephone purchase plan may be held
                       for up to 15 days until your funds for the purchase have
                       been received. If you participate in the telephone
                       redemption by wire/ACH plan, Acorn will send redemption
                       proceeds to your bank (or other financial institution)
                       account via wire or ACH transfer. Your bank may impose a
                       fee for the incoming wire. Payment by wire is usually
                       credited to your bank account on the next business day
                       after your call; payment by ACH is usually within two
                       business days.

                                                                              21
<PAGE>

 
Your Account continued

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

 . Acorn may suspend redemptions or postpone payment dates on days when the NYSE
  is closed (other than weekends or holidays), when trading on the NYSE is
  restricted, or as permitted by the SEC.

 . Certain accounts (such as trust accounts, corporate accounts and custodial
  accounts) may require documentation in addition to the redemption request.
  Call 1-800-962-1585 for more information.

 . If a check representing (1) redemption proceeds, (2) a withdrawal under the
  systematic withdrawal plan, or (3) a dividend/capital gains distribution is
  returned "undeliverable" or remains uncashed for 6 months, Acorn may cancel
  the check and reinvest the proceeds in the fund issuing the check at the NAV
  on the date of cancellation. In addition, after such 6-month period, (1) Acorn
  will terminate your systematic withdrawal plan and future withdrawals will
  occur only when requested, or (2) Acorn will automatically reinvest future
  dividends and distributions in your fund.

 . If the value of your account falls below $1,000 because you sold shares, Acorn
  reserves the right to close your account and send the proceeds to you. Acorn
  will redeem your shares at the NAV calculated on the day your account is
  closed.

  Acorn has elected to be governed by Rule 18f-1 under the Investment Company
  Act of 1940 pursuant to which it is obligated to redeem shares solely in cash
  up to the lesser of $250,000 or 1% of the NAV of a fund during any 90-day
  period for any one shareholder. Redemptions in excess of the above amounts
  will normally be paid in cash, but may be paid wholly or partly by a
  distribution in kind of securities. If a redemption is made in kind, the
  redeeming shareholder would bear any transaction costs incurred in selling the
  securities received.

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

Signature Guarantee

  In some cases, you will have to make your redemption request in writing, and
  will have to obtain a signature guarantee. A signature guarantee is designed
  to protect you and Acorn from fraudulent activities. This requirement applies
  to any of the following situations:

 . you request a change to your current account registration, including your
  name, address or are establishing or changing a TOD beneficiary;

 . you want to sell more than $50,000 in shares;

 . you want the check mailed to an address other than the address on your account
  registration;

 . your address of record was changed within the past 60 days;

 . you want the check made payable to someone other than the account owner; or

 . you want to sell shares, and you instruct Acorn to wire the proceeds to a bank
  or brokerage account, but you do not have the telephone redemption by wire
  plan on your account.

  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.

22
<PAGE>
 

Shareholder and Account Policies

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

Statements and Reports

  To keep you informed about your investment, Acorn sends you various account
  statements and reports, including:

 . Confirmation statements that verify a buy or sell transaction, unless that
  transaction is part of the automatic investment plan. Acorn will automatically
  confirm your automatic investment plan transactions on a quarterly basis
  unless you request otherwise by calling 1-800-962-1585.

 . Quarter-end and year-end consolidated account statements

 . Quarterly, semi-annual and annual Acorn Family of Funds reports

 . Average cost statements for certain types of accounts that sold shares during
  the year

  Duplicate statements may be sent to a third party if requested on the account
  application by the registered account owner or by calling 1-800-962-1585.

  If you need copies of your historical account information, please call 
  1-800-962-1585. There is a small charge to obtain historical account
  information for prior years.

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

Share Price

  The funds are open for business each day the NYSE is open. The offering price
  (the price to buy one share) and the redemption price (price to sell one
  share) are a fund's net asset value (NAV) calculated at the next Closing Time
  after Acorn (or an authorized broker-dealer or financial services company,
  some of whom may charge a fee for their services) receives your purchase or
  redemption order. Closing Time is the time of the close of regular session
  trading on the NYSE, which is usually 3:00 p.m. Central time but is sometimes
  earlier.

  Acorn must receive both your purchase money and your application by Closing
  Time for you to receive that day's price. Likewise, Acorn must receive your
  redemption request by Closing Time for you to receive that day's price.

  Note: Acorn requires one day to obtain your purchase money for a telephone
  purchase order; therefore, a telephone purchase made before Closing Time will
  get the next determined NAV.

  NAV A fund's NAV is the value of a single share of the fund. The NAV is
  computed by adding up the value of a fund's investments, cash, and other
  assets, subtracting its liabilities, and then dividing the result by the
  number of shares outstanding.

  Acorn generally values each fund's portfolio securities and assets on the
  basis of market quotations from the primary market in which they are traded.
  In cases when the quotations are not readily available, or the quotation is
  determined not to represent a fair value, Acorn will use a method that Acorn's
  trustees believe accurately reflects a fair value. Values of foreign
  securities are translated from the local currency into U.S. dollars using
  current exchange rates. Because of the different trading hours in various
  foreign markets, the calculation of NAV does not take place at the same time
  as the determination of the prices of many foreign securities held by the
  funds. These timing differences may have a significant effect on a fund's NAV.

                                                                              23
<PAGE>
 
Shareholder and Account Policies continued

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

Address Changes

You may easily change your address over a recorded telephone line by calling 
1-800-962-1585. Acorn will send written confirmation of the change to both your
old and new addresses. You may not make a telephone redemption for 60 days after
you change your address by phone. During those 60 days, you must request any
fund redemptions in writing, and your signature must be guaranteed.

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

General Information Pertaining to all Telephone Transactions

Acorn will not be responsible for any loss resulting from unauthorized
transactions if it follows reasonable procedures designed to verify the identity
of the caller. Those procedures may include recording the call, requesting
additional information, and sending written confirmation of telephone
transactions. You should verify the accuracy of telephone transactions
immediately upon receipt of your confirmation statement. If you do not want the
flexibility of telephone purchase and redemption for your account, decline those
services on your account application, or call 1-800-962-1585 for instructions.

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

Telephone Exchange Plan and Money Market Funds

The telephone exchange plan permits you to use the telephone to switch your
investment between one Acorn fund and another, or between an Acorn fund and a
money market mutual fund participating in the plan.

Currently, the money market mutual funds participating in the plan are the Reich
& Tang Funds. The Reich & Tang Funds are: Short Term Income Fund, Money Market
Portfolio; Short Term Income Fund, U.S. Government Portfolio; Daily Tax Free
Income Fund; California Daily Tax Free Income Fund; Connecticut Daily Tax Free
Income Fund; Florida Daily Municipal Income Fund; Michigan Daily Tax Free Income
Fund; New Jersey Daily Municipal Income Fund; New York Daily Tax Free Income
Fund; North Carolina Daily Municipal Income Fund; and Pennsylvania Daily
Municipal Income Fund.

Each of the Reich & Tang Funds is a no-load fund managed by Reich & Tang Asset
Management, L.P. and offers check writing privileges (for accounts other than
IRAs) in addition to the exchange plan. Only Short Term Income Fund, Money
Market Portfolio is available for IRA accounts.

Exchange requests must be received by times noted below to receive that day's
closing price.

 . To exchange between IRA accounts with Acorn or a participating money market
  fund, call 1-800-962-1585 before Closing Time.

 . To switch from one Acorn account into another, or from an Acorn account into a
  participating money market fund, call 1-800-962-1585 before Closing Time.

 . To switch from a participating money market fund to an Acorn fund, call 1-800-
  221-3079 before 11:00 a.m. Central time.

If we receive your call after the times noted above, we will process your
exchange at the NAV next calculated on the following business day.

Because of the time needed to exchange money between the Acorn funds and a
participating money market fund, you may not exchange into and out of a
participating money market fund on the same or successive days; there must be at
least one day between exchanges.

24
<PAGE>

- --------------------------------------------------------------------------------
 
Exchange Plan Restrictions

The Acorn funds do not permit market-timing and have adopted policies to
discourage this practice.

 . Generally, you will be permitted to make up to 4 round trip exchanges per year
  (a round trip is an exchange out of one fund into another fund, and then back
  again).

 . You may only exchange between accounts that are registered in the same name,
  address, and taxpayer identification number.

 . Shares of the fund you are exchanging into must be available for sale in your
  state.

 . If you are opening a new account by exchange, your exchange must be at least
  $1,000.

 . The exchange plan is not available for shares of a fund for which you have
  been issued certificates.

 . If your account is subject to backup withholding, you may not use the exchange
  plan.

 . Acorn may temporarily or permanently terminate the exchange plan privilege of
  any investor who makes excessive use of the plan. Excessive trading can hurt
  fund performance and shareholders.

 . Acorn may refuse exchange purchases by any person or group, if Acorn believes
  the purchase will be harmful to existing shareholders.

 . Before exchanging into a money market fund, you should read its prospectus.
  Call 1-800-9-ACORN-9 (1-800-922-6769) to obtain a prospectus for a
  participating money market fund.

 . Exchanges may result in tax consequences for you.

 . Acorn may terminate or modify the exchange plan at any time, but will try to
  give prior notice whenever it is reasonably possible.

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

Authorized Agents

Acorn may authorize certain financial service companies, broker-dealers or their
designees (authorized agents) to accept purchase, redemption, and exchange
requests from their clients on whose behalf the authorized agent holds shares of
the funds. For purchase orders placed through an authorized agent, a shareholder
will pay a fund's NAV next computed after the receipt by the authorized agent of
such purchase order, plus any applicable transaction charge imposed by the
agent. For redemption orders placed through an authorized agent, a shareholder
will receive redemption proceeds which reflect the NAV next computed after the
receipt by the authorized agent of the redemption order, less any redemption
fees imposed by the agent.

Some financial institutions that act as Acorn's agent, or that otherwise
maintain nominee accounts with the funds for their clients for whom they hold
fund shares, might charge a fee (usually a percentage of the average net assets
held in such accounts) for accounting, shareholder servicing, and distribution
services the institution provides with respect to the underlying fund shares.
WAM pays those fees.

                                                                              25
<PAGE>
 
Dividends, Capital Gains and Taxes
- --------------------------------------------------------------------------------
               Each fund distributes substantially all of its net income and net
               realized capital gains to shareholders each year. Normally, the
               funds pay distributions in June and December.
- --------------------------------------------------------------------------------
Distribution 
 Options       You may receive your fund dividend and/or capital gains
               distributions in several ways:

               Reinvestment Acorn will automatically reinvest your dividends and
               capital gains distributions in additional shares of your fund.
               (Acorn will assign this option to your account if you do not
               indicate a choice on your account application.)

               Income-only Acorn will automatically reinvest your capital gains
               distributions, but you may receive a check for each dividend. If
               you prefer, Acorn will send your dividend proceeds via ACH
               transfer directly to your bank or financial institution. (You
               must establish this feature at least 10 days prior to the
               distribution.)

               Cash Acorn will automatically send you a check for all dividends
               and capital gains. If you prefer, Acorn will send your
               distribution proceeds via ACH transfer directly to your bank or
               financial institution. (You must establish this feature at least
               10 days prior to the distribution.)

               Acorn will automatically reinvest distributions for IRA owners
               who are under 59-1/2 years old. A cash payment of a distribution
               is a withdrawal of IRA earnings, and is subject to taxes and
               potential income tax penalties for those under age 59-1/2. Once
               you reach 59-1/2 years old, and are eligible to withdraw the
               earnings from your IRA, you may request cash payment of
               distributions.

               Acorn will reinvest any distributions at the NAV at Closing Time
               on the reinvestment date (ex-dividend). For those not reinvesting
               their distributions, Acorn will normally begin mailing
               distribution checks on the payable date, which is usually one
               week after the ex-dividend date.

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

Taxes          As with any investment, you should carefully consider how your
               investment in a fund will be taxed. If your account is a tax-
               deferred or tax-exempt account (for example, an IRA or an
               employee benefit plan account), the following tax discussion does
               not apply. If your account is not tax-deferred or tax-exempt,
               however, you should be aware of the following tax rules:

               Taxes on Distributions Distributions are subject to federal
               income tax, and may also be subject to state or local taxes. Your
               distributions are taxable when they are paid, whether you receive
               them in cash or reinvest them in additional shares. Distributions
               declared in October, November or December of the prior year and
               paid in January are taxable as if they were paid on December 31.

               For federal tax purposes, income and short-term capital gains
               distributions are taxed as dividends (ordinary income); and long-
               term capital gains distributions are taxed as long-term capital
               gains. Every January, Acorn will send you and the IRS a statement
               called a Form 1099-DIV, which will show the amount of each
               taxable distribution you received in the previous year. A year-
               end tax guide will accompany your Form 1099. If the total
               distributions you received for the year are less than $10.00, you
               may not receive a Form 1099.

26
<PAGE>

- ----------------------------------------------------------------------------- 
     Taxes on Transactions Your redemptions--including exchanges between funds
     or into a money fund--are subject to capital gains tax. A capital gain or
     loss is the difference between the price you paid (cost) for your shares
     and the price receive when you sell them.

     Whenever you sell shares of a fund, Acorn will send you a confirmation
     statement showing how many shares you sold and at what price. Acorn will
     also send you a year-end statement every January, and an average cost
     statement every February (if applicable) for shares you redeemed, to assist
     you or your tax preparer. It is up to you or your tax preparer to determine
     whether any given sale resulted in a capital gain and, if so, the amount of
     tax you owe. Be sure to keep your regular account statements; the
     information they contain will be essential in calculating the amount of
     your capital gains.
- -------------------------------------------------------------------------------
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 Acorn
     International or Acorn Foreign Forty. The Acorn tax guide, which is mailed
     with your Form 1099-DIV each year, will contain detailed information about
     the foreign tax credit/deduction.

     When you sign your account application, you certify that your social
     security or taxpayer identification number is correct and that you are not
     subject to 31% backup withholding for failing to report income to the IRS.
     If you violate IRS regulations, the IRS can require Acorn to withhold 31%
     of your taxable distributions and redemption proceeds.


Fund Service Providers

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

     Transfer Agent and Custodian
     State Street Bank and Trust Company
     Attn: Acorn Family of Funds
     PO Box 8502
     Boston, MA 02266-8502

     Distributor
     WAM Brokerage Service, L.L.C.
     227 W. Monroe Street
     Suite 3000
     Chicago, IL 60606-5016

     Shares of the funds are offered for sale through WAM Brokerage Services,
     L.L.C. (WAM BD) without any sales commission or charges to the funds or
     their shareholders. WAM BD is wholly owned by WAM, the funds' investment
     advisor, and the investment advisor's general partner, Wanger Asset
     Management, Ltd. WAM pays all distribution expenses relating to the funds,
     including payment or reimbursement of any expenses incurred by WAM BD.

                                                                              27
<PAGE>
 
Financial Highlights

- -------------------------------------------------------------------------------
The following tables will help you better understand each fund's performance for
the past five years, or for the period from the date of a fund's commencement of
operations, if less than five years. They are excerpted from each fund's
financial statements for the fiscal year ended December 31, 1998, audited by
Ernst & Young LLP. Certain information reflects financial results for a single
fund share. The total returns in the table represent the rate that an investor
would have earned (or lost) on an investment in a fund (assuming reinvestment of
all dividends and distributions). You may obtain the complete financial
statements and auditor's report by calling 1-800-9-ACORN-9 (1-800-922-6769) and
requesting a free copy of the funds' latest annual shareholder report.

<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------- 
<S>                  <C>                                  <C>      <C>      <C>      <C>      <C>    
Acorn Fund           For a share outstanding throughout     1998     1997     1996     1995     1994
                     each year--years ended 12/31
ACRNX                -----------------------------------------------------------------------------------
                   . Net asset value, beginning of year   $16.99   $15.04   $13.60   $12.24   $13.95
               
                     Income from Investment Operations:
                     Net investment income                   .04      .15      .09      .11      .06
               
                     Net realized and unrealized gain
                     (loss) on investments, foreign
                     currency and futures                    .91     3.57     2.93     2.42    (1.10)
                     -----------------------------------------------------------------------------------
                   . Total from investment operations        .95     3.72     3.02     2.53    (1.04)
               
                     Less distributions:
                     Dividends from net investment
                     income                                 (.03)    (.16)    (.11)    (.09)    (.11)
               
                     Distributions from net realized
                     and unrealized gains reportable
                     for federal income taxes              (1.06)   (1.61)   (1.47)   (1.08)    (.56)
                     -----------------------------------------------------------------------------------
                   . Total distributions                   (1.09)   (1.77)   (1.58)   (1.17)    (.67)
               
               
                   . Net asset value, end of year         $16.85   $16.99   $15.04   $13.60   $12.24
               
                     -----------------------------------------------------------------------------------
                   . Total return                            6.0%    25.0%    22.6%    20.8%    (7.4%)
               
                     -----------------------------------------------------------------------------------
                     
                     Ratios/supplemental data:
                     -----------------------------------------------------------------------------------
                     Ratio of expenses to average net
                     assets                                  .84%     .56%     .57%     .57%     .62%
                     -----------------------------------------------------------------------------------
                     Ratio of net investment income
                     to average net assets                   .30%     .75%     .53%     .89%     .55%
                     ----------------------------------------------------------------------------------- 
                     Portfolio turnover rate                  24%      32%      33%      29%      18%
                     -----------------------------------------------------------------------------------
                     Net assets at end of period
                     (in millions)                        $3,549   $3,681   $2,842   $2,399   $1,983
</TABLE>

28
<PAGE>
 
<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------ 

Acorn International           For a share outstanding throughout     1998     1997     1996     1995     1994
                              each year--years ended 12/31
                              ----------------------------------------------------------------------------------
<S>                           <C>                                  <C>      <C>      <C>      <C>      <C>     
ACINX                       . Net asset value, beginning of year    $18.39   $19.61   $16.59   $15.24   $15.94
                     
                              Income from Investment Operations:
                              Net investment income                    .17      .40      .13      .16      .07
                     
                              Net realized and unrealized gain
                              (loss) on investments, foreign
                              currency and futures                    2.68     (.34)    3.29     1.20     (.67)
                              ----------------------------------------------------------------------------------
                            . Total from investment operations        2.85      .06     3.42     1.36     (.60)
                     
                              Less distributions:
                              Dividends from net investment
                              income                                  (.15)    (.38)    (.12)      --       --
                     
                              Distributions from net realized
                              and unrealized gains reportable
                              for federal income taxes                (.27)    (.90)    (.28)    (.01)    (.10)
                              ----------------------------------------------------------------------------------
                            . Total distributions                     (.42)   (1.28)    (.40)    (.01)    (.10)
                     
                            . Net asset value, end of year          $20.82   $18.39   $19.61   $16.59   $15.24
                     
                              ----------------------------------------------------------------------------------
                            . Total return                            15.4%     0.2%    20.7%     8.9%    (3.8%)
                     
                              ----------------------------------------------------------------------------------
                     
                              Ratios/supplemental data:
                              ----------------------------------------------------------------------------------
                              Ratio of expenses to average net
                              assets                                  1.12%    1.19%    1.17%    1.22%    1.24%
                              ----------------------------------------------------------------------------------
                              Ratio of net investment income
                              to average net assets                    .86%     .58%     .51%     .90%     .48%
                              ----------------------------------------------------------------------------------
                              Portfolio turnover rate                   37%      39%      34%      26%      20%
                              ----------------------------------------------------------------------------------
                              Net assets at end of period
                              (in millions)                         $1,725   $1,623   $1,773   $1,276   $1,363
</TABLE>

                                                                              29
<PAGE>
 
<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------------------------------------------------- 
Acorn USA            For a share outstanding throughout      Year Ended    Year Ended    Inception 9/4/96
                     each period                                1998        12/31/97     Through 12/31/96
                     -------------------------------------------------------------------------------------
<S>                  <C>                                     <C>           <C>          <C>           
AUSAX       
                   . Net asset value, beginning of period      $ 15.12      $ 11.65        $ 10.00
            
                     Income from investment operations:
                     Net investment loss (a)                      (.07)         (.07)         (.02)
            
                     Net realized and unrealized gain
                     on investments                                .87          3.83          1.67
                     -------------------------------------------------------------------------------------
                   . Total from investment operations              .80          3.76          1.65
            
                     Less distributions:
                     Dividends from net investment
                     income                                         --            --            --
            
                     Distributions from net realized
                     and unrealized gains reportable
                     for federal income taxes                    (1.12)         (.29)           --
                     -------------------------------------------------------------------------------------
                   . Total distributions                         (1.12)         (.29)           --
            
                   . Net asset value, end of period             $14.80     $   15.12      $  11.65
            
                     -------------------------------------------------------------------------------------
                   . Total return                                  5.8%         32.3%         16.5%
            
                     -------------------------------------------------------------------------------------
            
                     Ratios/supplemental data:
                     -------------------------------------------------------------------------------------
                     Ratio of expenses to average net
                     assets (b)                                   1.20%         1.35%         1.85%  *
                     -------------------------------------------------------------------------------------
                     Ratio of net investment loss
                     to average net assets                        (.42%)        (.49%)        (.99%) *
                     -------------------------------------------------------------------------------------
                     Portfolio turnover rate                        42%           33%           20%  *
                     -------------------------------------------------------------------------------------
                     Net assets at end of period
                     (in millions)                              $  281         $ 185        $   53
</TABLE>

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

                (b)  The ratio of expenses to average net assets for 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

30
<PAGE>
 
<TABLE>
<CAPTION>
<S>                   <C>                                                    <C>
- -----------------------------------------------------------------------------------------------
Acorn Twenty          For a share outstanding throughout                     Inception 11/23/98
                      the period                                             Through 12/31/98
                      -------------------------------------------------------------------------
ACTWX               . Net asset value, beginning of period                         $10.00

                      Income from Investment Operations:
                      Net investment income (a)                                       --

                      Net realized and unrealized gain on
                      investments                                                     .71
                      -------------------------------------------------------------------------
                    . Total from investment operations                                .71

                    . Net asset value, end of period                               $10.71

                      -------------------------------------------------------------------------
                    . Total return                                                    7.1%
                      -------------------------------------------------------------------------


                      Ratios/supplemental data:
                      -------------------------------------------------------------------------
                      Ratio of expenses to average net
                      assets (b)(c)                                                  1.41%
                      -------------------------------------------------------------------------
                      Ratio of net investment income
                      gain to average net assets (c)                                  .22%*
                      -------------------------------------------------------------------------
                      Portfolio turnover rate                                         173%*
                      -------------------------------------------------------------------------
                      Net assets at end of period
                      (in millions)                                                   $34
</TABLE>

     (a) Net investment income 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 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.

     (c) Acorn Twenty was reimbursed by the Advisor for certain net expenses
         from November 23, 1998 through December 31, 1998. 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.


     *Annualized

                                                                              31
<PAGE>
 
                                             
<TABLE>
<CAPTION>

<S>                       <C>                                                       <C>
- ------------------------------------------------------------------------------------------------------
Acorn                     For a share outstanding throughout                        Inception 11/23/98
Foreign Forty             the period                                                through 12/31/98
                          ----------------------------------------------------------------------------
                        . Net asset value, beginning of period                             $10.00
ACFFX
                          Income from Investment Operations:
                          Net investment loss (a)                                            (.01)

                          Net realized and unrealized gain on
                          investments                                                        1.01
                          ----------------------------------------------------------------------------
                        . Total from investment operations                                   1.00

                        . Net asset value, end of period                                   $11.00
                          ----------------------------------------------------------------------------
                        . Total return                                                       10.0%                        
                          ----------------------------------------------------------------------------


                          Ratio/supplemental data:
                          ----------------------------------------------------------------------------
                          Ratio of expenses to average net
                          assets (b)(c)                                                      1.73%*
                          ----------------------------------------------------------------------------
                          Ratio of net investment loss
                          to average net assets (c)                                          (.78%)*
                          ----------------------------------------------------------------------------
                          Portfolio turnover rate                                              90%*
                          ----------------------------------------------------------------------------
                          Net assets at end of period
                          (in millions)                                                       $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 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.

     (c) Acorn Twenty was reimbursed by the Advisor for certain net expenses
from November 23, 1998 through December 31, 1998. 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.

*Annualized

32
<PAGE>
 
Acorn Family of Funds

The Acorn Family of Funds' semi-annual and annual reports to shareholders
contain additional information about the funds. These reports provide commentary
on market conditions and investment strategies that affected each fund's
performance over the past six- and 12-month periods. The Statement of Additional
Information (also known as the SAI) also contains detailed information about the
Acorn funds' policies and operations. The SAI is incorporated in this prospectus
by reference. To obtain free copies of the funds' latest semi-annual and annual
shareholder reports, the funds' SAI, to request other information about a fund
or to make inquiries, simply call 1-800-9-ACORN 9 (1-800-922-6769) to make your
request, or write to The Acorn Family of Funds, PO Box 8502, Boston,
Massachusetts, 02266-8502.

You may also obtain this and other information about the Acorn funds directly
from the Securities and Exchange Commission (SEC). You may visit the SEC online
at http://www.sec.gov or in person at the SEC's Public Reference Room in
Washington, DC. You may also request information by calling the SEC at 1-800-
SEC-0330 (1-802-732-0330), or sending your request and the appropriate
duplicating fee to the SEC's Public Reference Section, Washington, DC 20549-
6009.

811-01829

<PAGE>
 



                            [PHOTO OF ACORNS HERE]
<PAGE>
 
                                                          ACORN INVESTMENT TRUST

                                                                    STATEMENT OF
                                                          ADDITIONAL INFORMATION
                                                                     May 1, 1999

                                                          227 West Monroe Street
                                                                      Suite 3000
                                                         Chicago, Illinois 60606
                                                                 1-800-9-ACORN-9
                                                                  1-800-922-6769

ACORN FUND
ACORN INTERNATIONAL
ACORN USA
ACORN TWENTY
ACORN FOREIGN FORTY

No-Load Funds
- -------------------------------------------------------------------------------
                               TABLE OF CONTENTS
                               -----------------

<TABLE>
<CAPTION>

                                                            Page
                                                            ----
 
<S>                                                         <C>
     Information About the Funds..........................    2
     Investment Objectives and Policies...................    2
     Investment Techniques and Risks......................    3
     Investment Restrictions..............................   21
     Performance Information..............................   27
     Investment Adviser...................................   30
     Distributor..........................................   32
     The Trust............................................   33
     Trustees and Officers................................   34
     Purchasing and Redeeming Shares......................   38
     Additional Tax Information...........................   39
     Taxation of Foreign Shareholders.....................   41
     Portfolio Transactions...............................   41
     Custodian............................................   43
     Independent Auditors.................................   44
     Appendix - Description of Bond Ratings...............   45
     Financial Statements.................................   47
</TABLE>
- --------------------------------------------------------------------------------

     This Statement of Additional Information ("SAI") is not a prospectus
but provides information that should be read in conjunction with the prospectus
of Acorn Fund, Acorn International, Acorn USA, Acorn Twenty and Acorn Foreign
Forty dated the date of this SAI and any supplement to the prospectus. A copy of
the Acorn Family of Funds 1998 annual report to shareholders accompanies this
SAI.  A copy of the prospectus and additional copies of the annual reports can
be obtained from Acorn at no charge by writing or telephoning Acorn at its
address or telephone number shown above.
<PAGE>
 
                          Information About the Funds

     Acorn Fund invests mostly in stocks of small and medium-size companies,
generally those with market capitalizations of less than $1 billion.  Of those
stocks, Acorn Fund invests mostly in U.S. companies, but also may have
significant foreign investments.

     Acorn International concentrates its investments in stocks of small and
medium-size non-U.S. companies, generally those with market capitalizations of
less than $1 billion.

     Acorn USA invests mostly in stocks of small and medium-sized U.S.
companies, generally those with market capitalizations of less than $1 billion.

     Acorn Twenty invests primarily in the stocks of U.S. companies with market
capitalizations of $1 billion to $10 billion.  Acorn Twenty is a non-diversified
fund that ordinarily focuses its investments in 20 to 25 U.S. companies.

     Acorn Foreign Forty invests for long-term capital growth.  The fund invests
primarily in the stocks of foreign companies with market capitalizations of $1
billion to $10 billion.  Acorn Foreign Forty is a non-diversified fund that
ordinarily has investments in 40 to 60 companies in developed markets.

     Acorn Fund, Acorn International and Acorn USA are diversified funds under
the federal securities laws.  Acorn Twenty  and Acorn Foreign Forty are non-
diversified under the federal securities laws.  However, each of the funds
complies with the diversification standards established by the tax laws.  See
"Investment Techniques and Risks - Diversification" for more information.

     The funds are series of Acorn Investment Trust ("Acorn" or the "Trust").
All five funds are currently open to new investors; however, Acorn reserves the
right to close one or more of the funds to new investors if the board of
trustees of Acorn determines that additional cash flow would be detrimental to
the management of the funds.

     The discussion below supplements the description in the prospectus of each
fund's investment objective, policies, and restrictions.

                       Investment Objectives and Policies

     Acorn Fund, Acorn International, Acorn USA, Acorn Twenty and Acorn Foreign
Forty invest with the objective of long-term growth of capital.  The funds are
not designed for investors seeking primarily income rather than capital
appreciation.  The funds are not, alone or together, a balanced investment
program, and there can be no assurance that any of the funds will achieve its
investment objective.

     The funds use the techniques and invest in the types of securities
described below and in the prospectus.

                                       2
<PAGE>
 
                        Investment Techniques and Risks

Common Stocks

     The funds invest mostly in common stocks, which represent an equity
interest (ownership) in a corporation.  This ownership interest often gives the
funds the right to vote on measures affecting the company's organization and
operations.  The funds also invest in other types of equity securities,
including preferred stocks and securities convertible into common stocks.  Over
time, common stocks have historically provided superior long-term capital growth
potential.  However, stock prices may decline over short or even extended
periods.  Stock markets tend to move in cycles, with periods of rising stock
prices and periods of falling stock prices.  As a result, the funds should be
considered long-term investments, designed to provide the best results when held
for several years or more.  The funds may not be suitable investments if you
have a short-term investment horizon or are unwilling to accept fluctuations in
share price, including significant declines over a given period.  Under normal
conditions, the funds' common stock investments (as a percent of total assets)
are allocated as follows:

<TABLE>
<CAPTION>
 
                          U.S.* Companies             Foreign
                                                     Companies
                      -----------------------------------------------
         Fund                 Maximum                 Maximum
- ---------------------------------------------------------------------
<S>                      <C>                  <C>
Acorn Fund                   100%                        33%
Acorn International           25%                       100%
    Acorn USA                100%                        10%
   Acorn Twenty              100%                        15%
Acorn Foreign Forty           15%                       100%
- ---------------------------------------------------------------------
</TABLE>
                                        

Acorn Twenty usually limits its investments in foreign companies to those whose
operations are primarily in the U.S.

*  For Acorn Foreign Forty, includes U.S. investments (usually limited to
companies whose operations are primarily overseas).

See also the discussion of foreign securities below.

Diversification

     Diversification is a means of reducing risk by investing in a broad range
of stocks or other securities.  Because Acorn Twenty and Acorn Foreign Forty are
non-diversified, those funds have the ability to take larger positions in a
smaller number of issuers.  The appreciation or depreciation of a single stock
may have a greater impact on the NAV of a non-diversified fund, because it is
likely to have a greater percentage of its assets invested in that stock.  As a
result, the share price of Acorn Twenty and Acorn Foreign Forty can be expected
to fluctuate more than that of broadly diversified funds investing in similar
securities.  Because they are non-diversified, those funds are not subject to
the limitations under the Investment Company Act of 1940 in the percentage of
their assets that they may invest in any one issuer.  Both funds, 

                                       3
<PAGE>
 
however, intend to comply with the diversification standards for regulated
investment companies under Subchapter M of the Internal Revenue Code summarized
under "Investment Restrictions").

Foreign Securities

     The funds invest in foreign securities, which may entail a greater degree
of risk (including risks relating to exchange rate fluctuations, tax provisions,
or expropriation of assets) than does investment in securities of domestic
issuers.  As noted above, under normal market conditions, each fund may invest
in foreign securities (as a percentage of total assets) as set forth below:

<TABLE>
<CAPTION>
 
                                 Foreign
                                Companies
                      --------------------------
         Fund                    Maximum
         ----                    -------
- ------------------------------------------------
<S>                      <C>
    Acorn Fund               33%
Acorn International         100%
    Acorn USA                10%
   Acorn Twenty              15%
Acorn Foreign Forty         100%
- ------------------------------------------------
</TABLE>

     Acorn Foreign Forty invests primarily in developed countries but may invest
up to 15% of its total assets in securities of companies with broad
international interests that are domiciled in the United States or in countries
considered "emerging markets," if the operations of those companies are located
primarily in developed overseas markets.  The Fund uses the terms "developed
markets" and "emerging markets" as those terms are defined by the International
Financial Corporation, a member of the World Bank Group ("IFC"). "Emerging
markets" as used by the Fund includes markets designated "frontier markets" by
the IFC.  The Fund does not intend to invest more than 5% of its total assets in
those countries included in the "emerging markets" or "frontier markets"
categories.

     The securities markets of emerging markets are substantially smaller, less
developed, less liquid, and more volatile than the securities markets of the
United States and other more developed countries.  Disclosure and regulatory
standards in many respects are less stringent than in the United States.  There
also may be a lower level of monitoring and regulation of emerging markets of
traders, insiders, and investors.  Enforcement of existing regulations has been
extremely limited.

     Acorn Twenty usually limits its investments in foreign companies to those
whose operations are primarily in the U.S.

     The funds may invest in securities of foreign issuers directly or in the
form of American Depositary Receipts (ADRs), European Depositary Receipts
(EDRs), Global Depositary Receipts (GDRs) or other securities representing
underlying shares of foreign issuers.  Positions in these securities are not
necessarily denominated in the same currency as the common stocks into which
they may be converted.  ADRs are receipts typically issued by an American bank
or trust company evidencing ownership of the underlying securities.  EDRs are
European receipts 

                                       4
<PAGE>
 
evidencing a similar arrangement. GDRs trade in both U.S. and non-U.S. markets.
Generally ADRs, in registered form, are designed for use in the U.S. securities
markets and EDRs, in bearer form, are designed for use in European securities
markets. The funds may invest in both "sponsored" and "unsponsored" depositary
receipts. In a sponsored depositary receipt, the issuer typically pays some or
all of the expenses of the depository and agrees to provide its regular
shareholder communications to depositary receipt holders. An unsponsored
depositary receipt is created independently of the issuer of the underlying
security. The depositary receipt holders generally pay the expenses of the
depository and do not have an undertaking from the issuer of the underlying
security to furnish shareholder communications. Therefore, in the case of an
unsponsored depositary receipt, a fund is likely to bear its proportionate share
of the expenses of the depository and it may have greater difficulty in
receiving shareholder communications than it would have with a sponsored
depositary receipt. None of the funds expects to invest 5% or more of its total
assets in unsponsored depositary receipt.

     The funds' investment performance is affected by the strength or weakness
of the U.S. dollar against the currencies of the foreign markets in which its
securities trade or in which they are denominated.  For example, if the dollar
falls in value relative to the Japanese yen, the dollar value of a yen-
denominated stock held in the portfolio will rise even though the price of the
stock remains unchanged.  Conversely, if the dollar rises in value relative to
the yen, the dollar value of the yen-denominated stock will fall.  (See
discussion of transaction hedging and portfolio hedging under "Currency Exchange
Transactions.")

     Investors should understand and consider carefully the risks involved in
foreign investing.  Investing in foreign securities, positions in which are
generally denominated in foreign currencies, and utilization of forward foreign
currency exchange contracts involve risks and opportunities not typically
associated with investing in U.S. securities.  These considerations include:
fluctuations in exchange rates of foreign currencies; possible imposition of
exchange control regulation or currency restrictions that would prevent cash
from being brought back to the United States; less public information with
respect to issuers of securities; less governmental supervision of stock
exchanges, securities brokers, and issuers of securities; lack of uniform
accounting, auditing, and financial reporting standards; lack of uniform
settlement periods and trading practices; less liquidity and frequently greater
price volatility in foreign markets than in the United States; possible
imposition of foreign taxes; possible investment in securities of companies in
developing as well as developed countries; and sometimes less advantageous
legal, operational, and financial protections applicable to foreign subcustodial
arrangements.  In addition, the costs of investing in foreign securities are
higher than the costs of investing in U.S. securities.

     Although the funds try to invest in companies and governments of countries
having stable political environments, there is the possibility of expropriation
or confiscatory taxation, seizure or nationalization of foreign bank deposits or
other assets, establishment of exchange controls, the adoption of foreign
government restrictions, or other adverse political, social, or diplomatic
developments that could affect investment in these nations.

                                       5
<PAGE>
 
     The countries in which the funds invest include those listed below.  A fund
may not invest in all the countries listed, and it may invest in other countries
as well, when such investments are consistent with that fund's investment
objective and policies.

<TABLE>
     Mature Markets           Developing Markets                Emerging Markets
     --------------          ------------------                ----------------
     <S>                     <C>                           <C>                 <C>
      Australia                   Argentina                Bangladesh          Morocco
      Austria                     Chile                    Botswana            Pakistan
      Belgium                     Greece                   Brazil              Peru
      Canada                      Hong Kong                China               Philippines
      Denmark                     Indonesia                Colombia            Poland
      Finland                     Israel                   Cyprus              Sri Lanka
      France                      Korea                    Czech Republic      Swaziland
      Germany                     Malaysia                 Ecuador             Turkey
      Ireland                     Mexico                   Egypt               Uruguay
      Italy                       Portugal                 Ghana               Venezuela
      Japan                       Singapore                Hungary             Zambia
      Luxembourg                  Taiwan                   India               Zimbabwe
      Netherlands                 Thailand                 Jordan
      New Zealand                                          Kenya
      Norway
      South Africa
      Spain
      Sweden
      Switzerland
      United Kingdom
      United States
</TABLE>


     It may not be feasible for the funds currently to invest in all of these
countries due to restricted access to their securities markets or inability to
implement satisfactory custodial arrangements.

Currency Exchange Transactions

     The funds may enter into currency exchange transactions.  A currency
exchange transaction may be conducted either on a spot (i.e., cash) basis at the
spot rate for purchasing or selling currency prevailing in the foreign exchange
market or through a forward currency exchange contract ("forward contract").  A
forward contract is an agreement to purchase or sell a specified currency at a
specified future date (or within a specified time period) and price set at the
time of the contract.  Forward contracts are usually entered into with banks,
foreign exchange dealers or broker-dealers, are not exchange-traded, and are
usually for less than one year, but may be renewed.

     Forward currency transactions may involve currencies of the different
countries in which the funds may invest, and serve as hedges against possible
variations in the exchange rate between these currencies.  The funds' currency
transactions are limited to transaction hedging and portfolio hedging involving
either specific transactions or portfolio positions, except to the extent
described below under "Synthetic Foreign Money Market Positions."  Transaction
hedging is the purchase or sale of a forward contract with respect to specific
payables or receivables of a fund accruing in connection with the purchase or
sale of portfolio securities.  

                                       6
<PAGE>
 
Portfolio hedging is the use of a forward contract with respect to a portfolio
security position denominated or quoted in a particular currency. The funds may
engage in portfolio hedging with respect to the currency of a particular country
in amounts approximating actual or anticipated positions in securities
denominated in that currency. When a fund owns or anticipates owning securities
in countries whose currencies are linked, Wanger Asset Management, L.P. ("WAM"),
the funds' investment adviser, may aggregate such positions as to the currency
hedged.

     If a fund enters into a forward contract hedging an anticipated purchase of
portfolio securities, assets of that fund having a value at least as great as
the fund's commitment under such forward contract will be segregated on the
books of the fund and held by the custodian while the contract is outstanding.

     At the maturity of a forward contract to deliver a particular currency, a
fund may either sell the portfolio security related to such contract and make
delivery of the currency, or it may retain the security and either acquire the
currency on the spot market or terminate its contractual obligation to deliver
the currency by purchasing an offsetting contract with the same currency trader
obligating it to purchase on the same maturity date the same amount of the
currency.

     It is impossible to forecast with absolute precision the market value of
portfolio securities at the expiration of a forward contract.  Accordingly, it
may be necessary for a fund to purchase additional currency on the spot market
(and bear the expense of such purchase) if the market value of the security is
less than the amount of currency that the fund is obligated to deliver and if a
decision is made to sell the security and make delivery of the currency.
Conversely, it may be necessary to sell on the spot market some of the currency
received upon the sale of the portfolio security if its market value exceeds the
amount of currency that fund is obligated to deliver.

     If a fund retains the portfolio security and engages in an offsetting
transaction, that fund will incur a gain or a loss to the extent that there has
been movement in forward contract prices.  If the fund engages in an offsetting
transaction, it may subsequently enter into a new forward contract to sell the
currency.  Should forward prices decline during the period between a fund's
entering into a forward contract for the sale of a currency and the date it
enters into an offsetting contract for the purchase of the currency, the fund
will realize a gain to the extent the price of the currency it has agreed to
sell exceeds the price of the currency it has agreed to purchase.  Should
forward prices increase, a fund will suffer a loss to the extent the price of
the currency it has agreed to purchase exceeds the price of the currency it has
agreed to sell.  A default on the contract would deprive the fund of unrealized
profits or force the fund to cover its commitments for purchase or sale of
currency, if any, at the current market price.

     Hedging against a decline in the value of a currency does not eliminate
fluctuations in the prices of portfolio securities or prevent losses if the
prices of such securities decline.  Such transactions also preclude the
opportunity for gain if the value of the hedged currency should rise.  Moreover,
it may not be possible for a fund to hedge against a devaluation that is so
generally anticipated that the fund is not able to contract to sell the currency
at a price above the devaluation level it anticipates.  The cost to a fund of
engaging in currency exchange transactions 

                                       7
<PAGE>
 
varies with such factors as the currency involved, the length of the contract
period, and prevailing market conditions. Since currency exchange transactions
are usually conducted on a principal basis, no fees or commissions are involved.

     Synthetic Foreign Money Market Positions.  The funds may invest in money
     ----------------------------------------                                
market instruments denominated in foreign currencies.  In addition to, or in
lieu of, such direct investment, the funds may construct a synthetic foreign
money market position by (a) purchasing a money market instrument denominated in
one currency (generally U.S. dollars) and (b) concurrently entering into a
forward contract to deliver a corresponding amount of that currency in exchange
for a different currency on a future date and at a specified rate of exchange.
For example, a synthetic money market position in Japanese yen could be
constructed by purchasing a U.S. dollar money market instrument, and entering
concurrently into a forward contract to deliver a corresponding amount of U.S.
dollars in exchange for Japanese yen on a specified date and at a specified rate
of exchange.  Because of the availability of a variety of highly liquid short-
term U.S. dollar money market instruments, a synthetic money market position
utilizing such U.S. dollar instruments may offer greater liquidity than direct
investment in foreign money market instruments.  The results of a direct
investment in a foreign currency and a concurrent construction of a synthetic
position in such foreign currency, in terms of both income yield and gain or
loss from changes in currency exchange rates, in general should be similar, but
would not be identical because the components of the alternative investments
would not be identical.  Except to the extent a synthetic foreign money market
position consists of a money market instrument denominated in a foreign
currency, the synthetic foreign money market position shall not be deemed a
"foreign security" for purposes of the investment limits set forth in the chart
on page 4.

Options and Futures

     The funds may purchase and write both call options and put options on
securities and on indexes, and enter into interest rate and index futures
contracts, and may purchase or sell options on such futures contracts ("futures
options") in order to provide additional revenue, or to hedge against changes in
security prices or interest rates.  The funds may also use other types of
options, futures contracts and futures options currently traded or subsequently
developed and traded, provided the board of trustees determines that their use
is consistent with the funds' investment objective.

     Options.  An option on a security (or index) is a contract that gives the
     -------                                                                  
purchaser (holder) of the option, in return for a premium, the right to buy from
(call) or sell to (put) the seller (writer) of the option the security
underlying the option (or the cash value of the index) at a specified exercise
price at any time during the term of the option (normally not exceeding nine
months).  The writer of an option on an individual security or on a foreign
currency has the obligation upon exercise of the option to deliver the
underlying security or foreign currency upon payment of the exercise price or to
pay the exercise price upon delivery of the underlying security or foreign
currency.  Upon exercise, the writer of an option on an index is obligated to
pay the difference between the cash value of the index and the exercise price
multiplied by the specified multiplier for the index option.  (An index is
designed to reflect specified facets of a 

                                       8
<PAGE>
 
particular financial or securities market, a specific group of financial
instruments or securities, or certain economic indicators.)

     The funds will write call options and put options only if they are
"covered."  For example, in the case of a call option on a security, the option
is "covered" if a fund owns the security underlying the call or has an absolute
and immediate right to acquire that security without additional consideration
(or, if additional consideration is required, assets having a value at least
equal to that amount are segregated on the books of a fund) upon conversion or
exchange of other securities held in its portfolio.

     If an option written by a fund expires, that fund realizes a capital gain
equal to the premium received at the time the option was written.  If an option
purchased by a fund expires, that fund realizes a capital loss equal to the
premium paid.

     Prior to the earlier of exercise or expiration, an option may be closed out
by an offsetting purchase or sale of an option of the same series (type,
exchange, underlying security or index, exercise price and expiration).  There
can be no assurance, however, that a closing purchase or sale transaction can be
effected when a fund desires.

     A fund will realize a capital gain from a closing purchase transaction if
the cost of the closing option is less than the premium received from writing
the option, or, if it is more, the fund will realize a capital loss.  If the
premium received from a closing sale transaction is more than the premium paid
to purchase the option, the fund will realize a capital gain or, if it is less,
the fund will realize a capital loss.  The principal factors affecting the
market value of a put or a call option include supply and demand, interest
rates, the current market price of the underlying security or index in relation
to the exercise price of the option, the volatility of the underlying security
or index, and the time remaining until the expiration date.

     A put or call option purchased by a fund is an asset of that fund, valued
initially at the premium paid for the option.  The premium received for an
option written by a fund is recorded as a deferred credit.  The value of an
option purchased or written is marked-to-market daily and is valued at the
closing price on the exchange on which it is traded or, if not traded on an
exchange or no closing price is available, at the mean between the last bid and
asked prices.

     OTC Derivatives.  The funds may buy and sell over-the-counter ("OTC")
     ---------------                                                      
derivatives.  Unlike exchange-traded derivatives, which are standardized with
respect to the underlying instrument, expiration date, contract size, and strike
price, the terms of OTC derivatives (derivatives not traded on exchanges)
generally are established through negotiation with the other party to the
contract.  While this type of arrangement allows a fund greater flexibility to
tailor an instrument to its needs, OTC derivatives generally involve greater
credit risk than exchange-traded derivatives, which are guaranteed by the
clearing organization of the exchanges where they are traded.  Each fund will
limit its investments so that no more than 5% of its total assets will be placed
at risk in the use of OTC derivatives.  See "Illiquid Securities" below for more
information on the risks associated with investing in OTC derivatives.

                                       9
<PAGE>
 
     Risks Associated with Options.  There are several risks associated with
     -----------------------------                                          
transactions in options.  For example, there are significant differences between
the securities markets, the currency markets, and the options markets that could
result in an imperfect correlation between these markets, causing a given
transaction not to achieve its objectives.  A decision as to whether, when, and
how to use options involves the exercise of skill and judgment, and even a well-
conceived transaction may be unsuccessful to some degree because of market
behavior or unexpected events.

     There can be no assurance that a liquid market will exist when a fund seeks
to close out an option position.  If a fund were unable to close out an option
that it had purchased on a security, it would have to exercise the option in
order to realize any profit or the option would expire and become worthless.  If
a fund were unable to close out a covered call option that it had written on a
security, it would not be able to sell the underlying security until the option
expired.  As the writer of a covered call option on a security, a fund foregoes,
during the option's life, the opportunity to profit from increases in the market
value of the security covering the call option above the sum of the premium and
the exercise price of the call.  As the writer of a covered call option on a
foreign currency, a fund foregoes, during the option's life, the opportunity to
profit from currency appreciation.

     If trading were suspended in an option purchased or written by one of the
funds, that fund would not able to close out the option.  If restrictions on
exercise were imposed, the fund might be unable to exercise an option it has
purchased.

     Futures Contracts and Options on Futures Contracts.  The funds may use
     --------------------------------------------------                    
interest rate futures contracts and index futures contracts.  An interest rate
or index futures contract provides for the future sale by one party and purchase
by another party of a specified quantity of a financial instrument or the cash
value of an index /1/ at a specified price and time.  A public market exists in
                   -   
futures contracts covering a number of indexes (including, but not limited to:
the Standard & Poor's 500 Index; the Value Line Composite Index; the Russell
2000 Index; and the New York Stock Exchange Composite Index) as well as
financial instruments (including, but not limited to: U.S. Treasury bonds; U.S.
Treasury notes; Eurodollar certificates of deposit; and foreign currencies).
Other index and financial instrument futures contracts are available and it is
expected that additional futures contracts will be developed and traded.

     The funds may purchase and write call and put futures options.  Futures
options possess many of the same characteristics as options on securities and
indexes (discussed above).  A futures option gives the holder the right, in
return for the premium paid, to assume a long 


__________________________________
/1/A futures contract on an index is an agreement pursuant to which two parties
 - 
agree to take or make delivery of an amount of cash equal to the difference
between the value of the index at the close of the last trading day of the
contract and the price at which the index contract was originally written.
Although the value of a securities index is a function of the value of certain
specified securities, no physical delivery of those securities is made.

                                       10
<PAGE>
 
position (call) or short position (put) in a futures contract at a specified
exercise price at any time during the period of the option. Upon exercise of a
call option, the holder acquires a long position in the futures contract and the
writer is assigned the opposite short position. In the case of a put option, the
opposite is true.

     To the extent required by regulatory authorities having jurisdiction over
the funds, the funds will limit their use of futures contracts and futures
options to hedging transactions.  For example, a fund might use futures
contracts to hedge against fluctuations in the general level of stock prices,
anticipated changes in interest rates, or currency fluctuations that might
adversely affect either the value of the fund's securities or the price of the
securities that the fund intends to purchase.  The fund's hedging may include
sales of futures contracts as an offset against the effect of expected declines
in stock prices or currency exchange rates or increases in interest rates and
purchases of futures contracts as an offset against the effect of expected
increases in stock prices or currency exchange rates or declines in interest
rates.  Although other techniques could be used to reduce the funds' exposure to
stock price, interest rate, and currency fluctuations, the funds may be able to
hedge their exposure more effectively and perhaps at a lower cost by using
futures contracts and futures options.

     The success of any hedging technique depends on WAM's ability to correctly
predict changes in the level and direction of stock prices, interest rates,
currency exchange rates, and other factors.  Should those predictions be
incorrect, a fund's return might have been better had hedging not been
attempted; however, in the absence of the ability to hedge, WAM might have taken
portfolio actions in anticipation of the same market movements with similar
investment results but, presumably, at greater transaction costs.

     When a purchase or sale of a futures contract is made by a fund, that fund
is required to deposit with its custodian or broker a specified amount of cash
or U.S. government securities or other securities acceptable to the broker
("initial margin").  The margin required for a futures contract is generally set
by the exchange on which the contract is traded; however, the margin requirement
may be modified during the term of the contract, and the fund's broker may
require margin deposits in excess of the minimum required by the exchange.  The
initial margin is in the nature of a performance bond or good faith deposit on
the futures contract, which is returned to the fund upon termination of the
contract, assuming all contractual obligations have been satisfied.  The funds
expect to earn interest income on their initial margin deposits.  A futures
contract held by a fund is valued daily at the official settlement price of the
exchange on which it is traded.  Each day the fund pays or receives cash, called
"variation margin," equal to the daily change in value of the futures contract.
This process is known as "marking-to-market."  Variation margin paid or received
by a fund does not represent a borrowing or loan by the fund but is instead
settlement between that fund and the broker of the amount one would owe the
other if the futures contract had expired at the close of the previous day.  In
computing daily net asset value ("NAV"), the funds will mark-to-market their
open futures positions.

     The funds are also required to deposit and maintain margin with respect to
put and call options on futures contracts they write.  Such margin deposits will
vary depending on the nature 

                                       11
<PAGE>
 
of the underlying futures contract (and the related initial margin
requirements), the current market value of the option, and other futures
positions held by the funds.

     Although some futures contracts call for making or taking delivery of the
underlying securities, usually these obligations are closed out prior to
delivery by offsetting purchases or sales of matching futures contracts (same
exchange, underlying security or index, and delivery month).  If an offsetting
purchase price is less than the original sale price, the funds realize a capital
gain, or if it is more, the funds realize a capital loss.  Conversely, if an
offsetting sale price is more than the original purchase price, the fund
engaging in the transaction realizes a capital gain, or if it is less, the fund
realizes a capital loss.  The transaction costs must also be included in these
calculations.

     Risks Associated with Futures.  There are several risks associated with the
     -----------------------------                                              
use of futures contracts and futures options as hedging techniques.  A purchase
or sale of a futures contract may result in losses in excess of the amount
invested in the futures contract.  There can be no guarantee that there will be
a correlation between price movements in the hedging vehicle and in the
portfolio securities being hedged.  In addition, there are significant
differences between the securities and futures markets that could result in an
imperfect correlation between the markets, causing a given hedge not to achieve
its objectives.  The degree of imperfection of correlation depends on
circumstances such as: variations in speculative market demand for futures,
futures options, and the related securities, including technical influences in
futures and futures options trading and differences between the funds'
investments being hedged and the securities underlying the standard contracts
available for trading.  For example, in the case of index futures contracts, the
composition of the index, including the issuers and the weighting of each issue,
may differ from the composition of a fund's portfolio, and, in the case of
interest rate futures contracts, the interest rate levels, maturities, and
creditworthiness of the issues underlying the futures contract may differ from
the financial instruments held in a fund's portfolio.  A decision as to whether,
when, and how to hedge involves the exercise of skill and judgment, and even a
well-conceived hedge may be unsuccessful to some degree because of market
behavior or unexpected stock price or interest rate trends.

     Futures exchanges may limit the amount of fluctuation permitted in certain
futures contract prices during a single trading day.  The daily limit
establishes the maximum amount that the price of a futures contract may vary
either up or down from the previous day's settlement price at the end of the
current trading session.  Once the daily limit has been reached in a futures
contract subject to the limit, no more trades may be made on that day at a price
beyond that limit.  The daily limit governs only price movements during a
particular trading day and therefore does not limit potential losses because the
limit may work to prevent the liquidation of unfavorable positions.  For
example, futures prices have occasionally moved to the daily limit for several
consecutive trading days with little or no trading, thereby preventing prompt
liquidation of positions and subjecting some holders of futures contracts to
substantial losses.  Stock index futures contracts are not normally subject to
such daily price change limitations.

     There can be no assurance that a liquid market will exist at a time when a
fund seeks to close out a futures or futures option position.  The fund would be
exposed to possible loss on the 

                                       12
<PAGE>
 
position during the interval of inability to close, and would continue to be
required to meet margin requirements until the position is closed. In addition,
many of the contracts discussed above are relatively new instruments without a
significant trading history. As a result, there can be no assurance that an
active secondary market will develop or continue to exist.

     Limitations on Options and Futures.  A fund will not enter into a futures
     ----------------------------------                                       
contract or purchase an option thereon if, immediately thereafter, the initial
margin deposits for futures contracts held by that fund plus premiums paid by it
for open futures option positions, less the amount by which any such positions
are "in-the-money," /2/ would exceed 5% of the fund's total assets.
                     -                                            

     When purchasing a futures contract or writing a put option on a futures
contract, a fund must maintain with its custodian or broker readily-marketable
securities having a fair market value (including any margin) at least equal to
the market value of such contract.  When writing a call option on a futures
contract, a fund similarly will maintain with its custodian readily-marketable
securities having a fair market value (including any margin) at least equal to
the amount by which such option is in-the-money until the option expires or is
closed out by the fund.

     A fund may not maintain open short positions in futures contracts, call
options written on futures contracts, or call options written on indexes if, in
the aggregate, the market value of all such open positions exceeds the current
value of the securities in its portfolio, plus or minus unrealized gains and
losses on the open positions, adjusted for the historical relative volatility of
the relationship between the portfolio and the positions.  For this purpose, to
the extent a fund has written call options on specific securities in its
portfolio, the value of those securities will be deducted from the current
market value of the securities portfolio.

     In order to comply with Commodity Futures Trading Commission Regulation 4.5
and thereby avoid being deemed a "commodity pool operator," the "underlying
commodity value" of each long position in a commodity contract in which a fund
invests will not at any time exceed the sum of:

     (1)  The value of short-term U.S. debt obligations or other U.S. dollar
          denominated high-quality short-term money market instruments and cash
          set aside in an identifiable manner, plus any funds deposited as
          margin on the contract;

     (2)  Unrealized appreciation on the contract held by the broker; and


______________________________
/2/A call option is "in-the-money" if the value of the futures contract that is
 -                                                                              
the subject of the option exceeds the exercise price.  A put option is "in-the-
money" if the exercise price exceeds the value of the futures contract that is
the subject of the option.

                                       13
<PAGE>
 
     (3)  Cash proceeds from existing investments due in not more than 30 days.

     "Underlying commodity value" means the size of the contract multiplied by
the daily settlement price of the contract.

     No fund will purchase puts, calls, straddles, spreads, or any combination
thereof if by reason of such purchase more than 10% of that fund's total assets
would be invested in such securities.

     Taxation of Options and Futures.    If a fund exercises a call or put
     --------------------------------                                     
option that it holds, the premium paid for the option is added to the cost basis
of the security purchased (call) or deducted from the proceeds of the security
sold (put).  For cash settlement options and futures options exercised by a
fund, the difference between the cash received at exercise and the premium paid
is a capital gain or loss.

     If a call or put option written by a fund is exercised, the premium is
included in the proceeds of the sale of the underlying security (call) or
reduces the cost basis of the security purchased (put).  For cash settlement
options and futures options written by a fund, the difference between the cash
paid at exercise and the premium received is a capital gain or loss.

     Entry into a closing purchase transaction will result in capital gain or
loss.  If an option written by a fund is in-the-money at the time it was written
and the security covering the option was held for more than the long-term
holding period prior to the writing of the option, any loss realized as a result
of a closing purchase transaction will be long-term.  The holding period of the
securities covering an in-the-money option will not include the period of time
the option is outstanding.

     If a fund writes an equity call option/3/ other than a "qualified covered
call option," as defined in the Internal Revenue Code, any loss on such option
transaction, to the extent it does not exceed the unrealized gains on the
securities covering the option, may be subject to deferral until the securities
covering the option have been sold.


     A futures contract held until delivery results in capital gain or loss
equal to the difference between the price at which the futures contract was
entered into and the settlement price on the earlier of delivery notice date or
expiration date.  If a fund delivers securities under a futures contract, the
fund also realizes a capital gain or loss on those securities.




___________________________
/3/An equity option is defined to mean any option to buy or sell stock, and any
 -                                                                              
other option the value of which is determined by reference to an index of stocks
of the type that is ineligible to be traded on a commodity futures exchange
(e.g., an option contract on a sub-index based on the price of nine hotel-casino
stocks).  The definition of equity option excludes options on broad-based stock
indexes (such as the Standard & Poor's 500 index).

                                       14
<PAGE>
 
     For federal income tax purposes, a fund generally is required to recognize
for each taxable year its net unrealized gains and losses as of the end of the
year on futures, futures options and non-equity options positions ("year-end
mark-to-market").  Generally, any gain or loss recognized with respect to such
positions (either by year-end mark-to-market or by actual closing of the
positions) is considered to be 60% long-term and 40% short-term, without regard
to the holding periods of the contracts.  However, in the case of positions
classified as part of a "mixed straddle," the recognition of losses on certain
positions (including options, futures and futures options positions, the related
securities and certain successor positions thereto) may be deferred to a later
taxable year.  Sale of futures contracts or writing of call options (or futures
call options) or buying put options (or futures put options) that are intended
to hedge against a change in the value of securities held by a fund may affect
the holding period of the hedged securities.

     If a fund were to enter into a short index future, short index futures
option or short index option position and the fund's portfolio were deemed to
"mimic" the performance of the index underlying such contract, the option or
futures contract position and the fund's stock positions may be deemed to be
positions in a mixed straddle, subject to the above-mentioned loss deferral
rules.

     The Taxpayer Relief Act of 1997 (the "Act") imposed constructive sale
treatment for federal income tax purposes on certain hedging strategies with
respect to appreciated securities.  Under these rules taxpayers will recognize
gain, but not loss, with respect to securities if they enter into short sales or
"offsetting notional principal contracts" (as defined by the Act) with respect
to, or futures or "forward contracts" (as defined by the Act) with respect to,
the same or substantially identical property, or if they enter into such
transactions and then acquire the same or substantially identical property.  The
Secretary of the Treasury is authorized to promulgate regulations that will
treat as constructive sales certain transactions that have substantially the
same effect as short sales, offsetting notional principal contracts, and futures
or forward contracts to deliver the same or substantially similar property.

     In order for the funds to continue to qualify for federal income tax
treatment as regulated investment companies, at least 90% of each fund's gross
income for a taxable year must be derived from qualifying income, i.e.,
dividends, interest, income derived from loans of securities, and gains from the
sale of securities or foreign currencies, or other income (including but not
limited to gains from options, futures, or forward contracts).  Any net gain
realized from futures (or futures options) contracts will be considered gain
from the sale of securities and therefore be qualifying income for purposes of
the 90% requirement.

     The funds intend to distribute to shareholders annually any capital gains
that have been recognized for federal income tax purposes (including year-end
mark-to-market gains) on options and futures transactions, together with gains
on other fund investments, to the extent such gains exceed recognized capital
losses and any net capital loss carryovers of the funds.   Shareholders will be
advised of the nature of such capital gain distributions.

     For further information, see the discussion under "Additional Tax
Information."

                                       15
<PAGE>
 
     Swap Agreements.  A swap agreement is generally individually negotiated and
     ----------------                                                           
structured to include exposure to a variety of different types of investments or
market factors.  Depending on its structure, a swap agreement may increase or
decrease a fund's exposure to changes in the value of an index of securities in
which the fund might invest, the value of a particular security or group of
securities, or foreign currency values.  Swap agreements can take many different
forms and are known by a variety of names.  A fund may enter into any form of
swap agreement if WAM determines it is consistent with that fund's investment
objective and policies, but each fund will limit its use of swap agreements so
that no more than 5% of its total assets will be invested in such agreements.

     A swap agreement tends to shift a fund's investment exposure from one type
of investment to another.  For example, if a fund agrees to exchange payments in
dollars at a fixed rate for payments in a foreign currency the amount of which
is determined by movements of a foreign securities index, the swap agreement
would tend to increase that fund's exposure to foreign stock market movements
and foreign currencies.  Depending on how it is used, a swap agreement may
increase or decrease the overall volatility of a fund's investments and its NAV.

     The performance of a swap agreement is determined by the change in the
specific currency, market index, security, or other factors that determine the
amounts of payments due to and from a fund.  If a swap agreement calls for
payments by a fund, that fund must be prepared to make such payments when due.
If the counterparty's creditworthiness declines, the value of a swap agreement
would be likely to decline, potentially resulting in a loss.  WAM expects to be
able to eliminate a fund's exposure under any swap agreement either by
assignment or by other disposition, or by entering into an offsetting swap
agreement with the same party or a similarly creditworthy party.

     A fund will segregate its assets to cover its current obligations under a
swap agreement.  If a fund enters into a swap agreement on a net basis, it will
segregate assets with a daily value at least equal to the excess, if any, of
that fund's accumulated obligations under the swap agreement over the
accumulated amount the fund is entitled to receive under the agreement.  If a
fund enters into a swap agreement on other than a net basis, it will segregate
assets with a value equal to the full amount of that fund's accumulated
obligations under the agreement.

Short Sales Against the Box

     Each fund may make short sales of securities if at all times, when a short
position is open, the fund owns an equal amount of such securities or securities
convertible into or exchangeable for, without payment of any further
consideration, securities of the same issue as, and equal in amount to, the
securities sold short.  This technique is called selling short "against the
box."  Although permitted by its investment restrictions, the Funds do not
currently intend to sell securities short.

     In a short sale against the box, a fund does not deliver from its portfolio
the securities sold and does not receive immediately the proceeds from the short
sale.  Instead, the fund borrows the securities sold short from a broker-dealer
through which the short sale is executed, and the broker-dealer delivers such
securities, on behalf of the fund, to the purchaser of such 

                                       16
<PAGE>
 
securities. Such broker-dealer is entitled to retain the proceeds from the short
sale until the fund delivers to such broker-dealer the securities sold short. In
addition, the fund is required to pay to the broker-dealer the amount of any
dividends paid on shares sold short. Finally, to secure its obligation to
deliver to such broker-dealer the securities sold short, the fund must deposit
and continuously maintain in a separate account with State Street an equivalent
amount of the securities sold short or securities convertible into or
exchangeable for such securities without the payment of additional
consideration. The fund is said to have a short position in the securities sold
until it delivers to the broker-dealer the securities sold, at which time the
fund receives the proceeds of the sale. Because the fund ordinarily will want to
continue to hold securities in its portfolio that are sold short, the fund will
normally close out a short position by purchasing on the open market and
delivering to the broker-dealer an equal amount of the securities sold short,
rather than by delivering portfolio securities.

     Short sales may protect a fund against the risk of losses in the value of
its portfolio securities because any unrealized losses with respect to such
portfolio securities should be wholly or partially offset by a corresponding
gain in the short position.  However, any potential gains in such portfolio
securities should be wholly or partially offset by a corresponding loss in the
short position.  The extent to which such gains or losses are offset will depend
upon the amount of securities sold short relative to the amount the fund owns,
either directly or indirectly, and, in the case where the fund owns convertible
securities, changes in the conversion premium.  The funds will incur transaction
costs in connection with short sales.

     In addition to enabling the funds to hedge against market risk, short sales
may afford a fund an opportunity to earn additional current income to the extent
the fund is able to enter into arrangements with broker-dealers through which
the short sales are executed to receive income with respect to the proceeds of
the short sales during the period the fund's short positions remain open.

     The Taxpayer Relief Act of 1997 imposed constructive sale treatment for
federal income tax purposes on certain hedging strategies with respect to
appreciated securities.  Under these rules taxpayers will recognize gain, but
not loss, with respect to securities if they enter into short sales of
"offsetting notional principal contracts" (as defined by the Act) with respect
to the same or substantially identical property, or if they enter into such
transactions and then acquire the same or substantially identical property.  The
Secretary of the Treasury is authorized to promulgate regulations that will
treat as constructive sales certain transactions that have substantially the
same effect as short sales.

Debt Securities

     The funds may invest in debt securities, including lower-rated securities
(i.e., securities rated BB or lower by Standard & Poor's Corporation ("S&P") or
Ba or lower by Moody's Investor Services, Inc. ("Moody's"), commonly called
"junk bonds"), and securities that are not rated.  There are no restrictions as
to the ratings of debt securities acquired by the funds or the portion of a
fund's assets that may be invested in debt securities in a particular ratings
category, except that Acorn International may not invest more than 20% of its
assets in securities rated 

                                       17
<PAGE>
 
below investment grade or considered by the Adviser to be of comparable credit
quality. Neither Acorn Fund nor Acorn International expects to invest more than
5% of its net assets in such securities during the current fiscal year. Acorn
USA, Acorn Twenty and Acorn Foreign Forty does not intend to invest more than
20% of its total assets in debt securities nor more than 5% of its total assets
in securities rated at or lower than the lowest investment grade.

     Securities rated BBB or Baa are considered to be medium grade and to have
speculative characteristics.  Lower-rated debt securities are predominantly
speculative with respect to the issuer's capacity to pay interest and repay
principal.  Investment in medium- or lower-quality debt securities involves
greater investment risk, including the possibility of issuer default or
bankruptcy.  An economic downturn could severely disrupt the market for such
securities and adversely affect the value of such securities.  In addition,
lower-quality bonds are less sensitive to interest rate changes than higher-
quality instruments and generally are more sensitive to adverse economic changes
or individual corporate developments.  During a period of adverse economic
changes, including a period of rising interest rates, the junk bond market may
be severely disrupted, and issuers of such bonds may experience difficulty in
servicing their principal and interest payment obligations.

     Medium- and lower-quality debt securities may be less marketable than
higher-quality debt securities because the market for them is less broad.  The
market for unrated debt securities is even narrower.  During periods of thin
trading in these markets, the spread between bid and asked prices is likely to
increase significantly, and a fund may have greater difficulty selling its
portfolio securities.  See "Purchasing and Redeeming Shares - Net Asset Value."
The market value of these securities and their liquidity may be affected by
adverse publicity and investor perceptions.  A more complete description of the
characteristics of bonds in each ratings category is included in the appendix to
this SAI.

Illiquid Securities

     The funds may not invest in illiquid securities, including restricted
securities and OTC derivatives, if as a result they would comprise more than 10%
of the value of the net assets of Acorn Fund, or more than 15% of the value of
the net assets of each of Acorn International, Acorn USA, Acorn Twenty and Acorn
Foreign Forty.

     Restricted securities may be sold only in privately negotiated transactions
or in a public offering with respect to which a registration statement is in
effect under the Securities Act of 1933 (the "1933 Act").  Where registration is
required, a fund may be obligated to pay all or part of the registration
expenses and a considerable period may elapse between the time of the decision
to sell and the time the fund may be permitted to sell a security under an
effective registration statement.  If, during such a period, adverse market
conditions were to develop, the fund might obtain a less favorable price than
prevailed when it decided to sell.  Restricted securities will be priced at a
fair value as determined in good faith by the board of trustees.  If, through
the appreciation of illiquid securities or the depreciation of liquid
securities, Acorn Fund should be in a position where more than 10% of the value
of its net assets are invested in illiquid assets, including restricted
securities and OTC derivatives (or more than 15% of the 

                                       18
<PAGE>
 
value of the net assets of each of Acorn International, Acorn USA, Acorn Twenty
and Acorn Foreign Forty), that fund will take appropriate steps to protect
liquidity.

     Notwithstanding the above, a fund may purchase securities that have been
privately placed but that are eligible for purchase and sale under Rule 144A
under the 1933 Act.  That rule permits certain qualified institutional buyers,
such as the funds, to trade in privately placed securities that have not been
registered for sale under the 1933 Act.  WAM, under the supervision of the board
of trustees, will consider whether securities purchased under Rule 144A are
illiquid and thus subject to a fund's restriction of investing no more than 10%
(for Acorn Fund) or 15% (for Acorn International, Acorn USA, Acorn Twenty and
Acorn Foreign Forty) of its assets in illiquid securities.  A determination of
whether a Rule 144A security is liquid or not is a question of fact.  In making
this determination WAM will consider the trading markets for the specific
security taking into account the unregistered nature of a Rule 144A security.
In addition, WAM could consider the (1) frequency of trades and quotes, (2)
number of dealers and potential purchasers, (3) dealer undertakings to make a
market, and (4) nature of the security and of market place trades (e.g., the
time needed to dispose of the security, the method of soliciting offers and the
mechanics of transfer).  The liquidity of Rule 144A securities would be
monitored and if, as a result of changed conditions, it is determined that a
Rule 144A security is no longer liquid, the funds' holdings of illiquid
securities would be reviewed to determine what, if any, steps are required to
assure that a fund does not invest more than the specified percentage of its
assets in illiquid securities.  Investing in Rule 144A securities could have the
effect of increasing the amount of a fund's assets invested in illiquid
securities if qualified institutional buyers are unwilling to purchase such
securities.

Repurchase Agreements

     Repurchase agreements are transactions in which a fund purchases a security
from a bank or recognized securities dealer and simultaneously commits to resell
that security to the bank or dealer at an agreed-upon price, date, and market
rate of interest unrelated to the coupon rate or maturity of the purchased
security.  Although repurchase agreements carry certain risks not associated
with direct investments in securities, a fund will enter into repurchase
agreements only with banks and dealers WAM believes present minimum credit risks
in accordance with guidelines approved by the board of trustees.  WAM will
review and monitor the creditworthiness of such institutions, and will consider
the capitalization of the institution, WAM's prior dealings with the
institution, any rating of the institution's senior long-term debt by
independent rating agencies, and other relevant factors.

     A fund will invest only in repurchase agreements collateralized at all
times in an amount at least equal to the repurchase price plus accrued interest.
To the extent that the proceeds from any sale of such collateral upon a default
in the obligation to repurchase were less than the repurchase price, the fund
would suffer a loss.  If the financial institution which is party to the
repurchase agreement petitions for bankruptcy or otherwise becomes subject to
bankruptcy or other liquidation proceedings there may be restrictions on a
fund's ability to sell the collateral and the fund could suffer a loss.
However, with respect to financial institutions whose bankruptcy or 

                                       19
<PAGE>
 
liquidation proceedings are subject to the U.S. Bankruptcy Code, each fund
intends to comply with provisions under such Code that would allow it
immediately to resell such collateral.

     At present, Acorn USA, Acorn Twenty and Acorn Foreign Forty are the only
funds that invest in repurchase agreements, and then only with respect to not
more than 5% of their respective total assets.  Acorn Fund and Acorn
International have no present intention of investing in repurchase agreements.

When-Issued and Delayed Delivery Securities; Reverse Repurchase Agreements

     The funds may purchase securities on a when-issued or delayed delivery
basis.  Although the payment and interest terms of these securities are
established at the time the fund enters into the commitment, the securities may
be delivered and paid for a month or more after the date of purchase, when their
value may have changed.  A fund makes such commitments only with the intention
of actually acquiring the securities, but may sell the securities before the
settlement date if WAM deems it advisable for investment reasons.  A fund may
utilize spot and forward foreign currency exchange transactions to reduce the
risk inherent in fluctuations in the exchange rate between one currency and
another when securities are purchased or sold on a when-issued or delayed
delivery basis.

     A fund may enter into reverse repurchase agreements with banks and
securities dealers.  A reverse repurchase agreement is a repurchase agreement in
which the fund is the seller of, rather than the investor in, securities and
agrees to repurchase them at an agreed-upon time and price.  Use of a reverse
repurchase agreement may be preferable to a regular sale and later repurchase of
securities because it avoids certain market risks and transaction costs.

     At the time a fund enters into a binding obligation to purchase securities
on a when-issued basis or enters into a reverse repurchase agreement, assets of
the fund having a value at least as great as the purchase price of the
securities to be purchased will be segregated on the books of the fund and held
by the custodian throughout the period of the obligation.  The use of these
investment strategies, as well as any borrowing by a fund, may increase NAV
fluctuation.  The funds have no present intention of investing in reverse
repurchase agreements.

Temporary Strategies

     The funds have the flexibility to respond promptly to changes in market and
economic conditions.  In the interest of preserving shareholders' capital, WAM
may employ a temporary defensive investment strategy if it determines such a
strategy to be warranted.  Pursuant to such a defensive strategy, a fund
temporarily may hold cash (U.S. dollars, foreign currencies, multinational
currency units) and/or invest up to 100% of its assets in high quality debt
securities or money market instruments of U.S. issuers (or, in the case of Acorn
Fund, Acorn International and Acorn Foreign Forty, those of foreign issuers),
and most or all of the fund's investments may be made in the United States and
denominated in U.S. dollars.  It is impossible to predict whether, when, or for
how long a fund might employ defensive strategies.

                                       20
<PAGE>
 
     In addition, pending investment of proceeds from new sales of fund shares
or to meet ordinary daily cash needs, a fund temporarily may hold cash (U.S.
dollars, foreign currencies, or multinational currency units) and may invest any
portion of its assets in money market instruments.

Portfolio Turnover

     Although the funds do not purchase securities with a view to rapid
turnover, there are no limitations on the length of time that portfolio
securities must be held.  Portfolio turnover can occur for a number of reasons
such as general conditions in the securities markets, more favorable investment
opportunities in other securities, or other factors relating to the desirability
of holding or changing a portfolio investment.  Under normal conditions, the
funds' portfolio turnover rate will be below 50%.  A high rate of portfolio
turnover, if it should occur, would result in increased transaction expenses
which must be borne by each fund.  High portfolio turnover may also result in
the realization of capital gains or losses and, to the extent net short-term
capital gains are realized, any distributions resulting from such gains will be
considered ordinary income for federal income tax purposes.

Line of Credit

     Acorn maintains a line of credit with a bank in order to permit borrowing
on a temporary basis to meet share redemption requests in circumstances in which
temporary borrowing may be preferable to liquidation of portfolio securities.
Any borrowings under that line of credit by the funds would be subject to each
fund's restrictions on borrowing under "Investment Restrictions," below.


                            Investment Restrictions

Acorn Fund
     In pursuing its investment objective Acorn Fund will not:


     1.   Invest more than 5% of its assets (valued at time of investment) in
     securities of any one issuer, except in government obligations;

     2.   Acquire securities of any one issuer which at the time of investment
          (a) represent more than 10% of the voting securities of the issuer or
          (b) have a value greater than 10% of the outstanding securities of
          the issuer;
              
     3.   Invest more than 25% of its assets (valued at time of investment) in
          securities of companies in any one industry;

     4.   Invest more than 5% of its assets (valued at time of investment) in
          securities of issuers with less than three years' operation (including
          predecessors);

                                       21
<PAGE>
 
     5.  Purchase or retain securities of a company if all of the trustees and
     officers of the Trust and of its investment adviser who individually own
     beneficially more than 1/2% of the securities of the company collectively
     own beneficially more than 5% of such securities;

     6.  Borrow money except (a) from banks for temporary or emergency purposes
     at fixed rates of interest in amounts not exceeding 10% of the value of the
     fund's assets at the time of borrowing, and (b) in connection with
     transactions in options and in securities index futures [the fund will not
     purchase additional securities when its borrowings, less amounts receivable
     on sales of portfolio securities, exceed 5% of total assets];

     7.  Pledge, mortgage or hypothecate its assets, except for temporary or
     emergency purposes and then to an extent not greater than 15% of its assets
     at cost, and except in connection with transactions in options and in
     securities index futures;

     8.  Underwrite the distribution of securities of other issuers; however the
     fund may acquire "restricted" securities which, in the event of a resale,
     might be required to be registered under the Securities Act of 1933 on the
     ground that the fund could be regarded as an underwriter as defined by that
     act with respect to such resale; but the fund will limit its total
     investment in restricted securities and in other securities for which there
     is no ready market to not more than 10% of its total assets at the time of
     acquisition;

     9.  Purchase and sell real estate or interests in real estate, although it
     may invest in marketable securities of enterprises which invest in real
     estate or interests in real estate;

     10.  Purchase and sell commodities or commodity contracts, except that it
     may enter into (a) futures and options on futures and (b) forward
     contracts;

     11.  Make margin purchases of securities, except for use of such short-term
     credits as are needed for clearance of transactions and except in
     connection with transactions in options, futures and options on futures;

     12.  Sell securities short or maintain a short position, except short sales
     against-the-box;

     13.  Participate in a joint or on a joint or several basis in any trading
     account in securities;

     14.  Invest in companies for the purpose of management or the exercise of
     control;

     15.  Issue any senior security except to the extent permitted under the
     Investment Company Act of 1940.

                                       22
<PAGE>
 
     It is also a fundamental policy of Acorn Fund to make loans to the extent
that investment in debt securities may be considered to constitute the making of
loans (subject to the 10% limitation stated in restriction 8 above).

Acorn International

     In pursuing its investment objective Acorn International will not:

     1.  With respect to 75% of the value of the fund's total assets, invest
     more than 5% of its total assets (valued at time of investment) in
     securities of a single issuer, except securities issued or guaranteed by
     the government of the U.S., or any of its agencies or instrumentalities;

     2.  Acquire securities of any one issuer that at the time of investment (a)
     represent more than 10% of the voting securities of the issuer or (b) have
     a value greater than 10% of the value of the outstanding securities of the
     issuer;

     3.  Invest more than 25% of its assets (valued at time of investment) in
     securities of companies in any one industry;

     4.  Make loans, but this restriction shall not prevent the fund from (a)
     buying a part of an issue of bonds, debentures, or other obligations that
     are publicly distributed, or from investing up to an aggregate of 15% of
     its total assets (taken at market value at the time of each purchase) in
     parts of issues of bonds, debentures or other obligations of a type
     privately placed with financial institutions, (b) investing in repurchase
     agreements, or (c) lending portfolio securities, provided that it may not
     lend securities if, as a result, the aggregate value of all securities
     loaned would exceed 33% of its total assets (taken at market value at the
     time of such loan);

     5.  Borrow money except (a) from banks for temporary or emergency purposes
     in amounts not exceeding 10% of the value of the fund's total assets at the
     time of borrowing, and (b) in connection with transactions in options,
     futures and options on futures. [The fund will not purchase additional
     securities when its borrowings, less amounts receivable on sales of
     portfolio securities, exceed 5% of total assets.];

     6.  Underwrite the distribution of securities of other issuers; however the
     fund may acquire "restricted" securities which, in the event of a resale,
     might be required to be registered under the Securities Act of 1933 on the
     ground that the fund could be regarded as an underwriter as defined by that
     act with respect to such resale; but the fund will limit its total
     investment in restricted securities and in other securities for which there
     is no ready market, including repurchase agreements maturing in more than
     seven days, to not more than 15% of its total assets at the time of
     acquisition;

     7.  Purchase and sell real estate or interests in real estate, although it
     may invest in marketable securities of enterprises that invest in real
     estate or interests in real estate;

                                       23
<PAGE>
 
     8.  Purchase and sell commodities or commodity contracts, except that it
     may enter into (a) futures and options on futures and (b) forward
     contracts;

     9.  Make margin purchases of securities, except for use of such short-term
     credits as are needed for clearance of transactions and except in
     connection with transactions in options, futures and options on futures;

     10.  Sell securities short or maintain a short position, except short sales
     against-the-box.

     11.  Issue any senior security except to the extent permitted under the
     Investment Company Act of 1940.

Acorn USA

     In pursuing its investment objective Acorn USA will not:

     1.  With respect to 75% of the value of the Fund's total assets, invest
     more than 5% of its total assets (valued at time of investment) in
     securities of a single issuer, except securities issued or guaranteed by
     the government of the U.S., or any of its agencies or instrumentalities;

     2.  Acquire securities of any one issuer which at the time of investment
     (a) represent more than 10% of the voting securities of the issuer or (b)
     have a value greater than 10% of the value of the outstanding securities of
     the issuer;

     3.  Invest more than 25% of its assets (valued at time of investment) in
     securities of companies in any one industry, except that this restriction
     does not apply to investments in U.S. government securities;

     4.  Make loans, but this restriction shall not prevent the Fund from (a)
     buying a part of an issue of bonds, debentures, or other obligations that
     are publicly distributed, or from investing up to an aggregate of 15% of
     its total assets (taken at market value at the time of each purchase) in
     parts of issues of bonds, debentures or other obligations of a type
     privately placed with financial institutions, (b) investing in repurchase
     agreements, or (c) lending portfolio securities, provided that it may not
     lend securities if, as a result, the aggregate value of all securities
     loaned would exceed 33% of its total assets (taken at market value at the
     time of such loan);

     5.  Borrow money except (a) from banks for temporary or emergency purposes
     in amounts not exceeding 33% of the value of the Fund's total assets at the
     time of borrowing, and (b) in connection with transactions in options,
     futures and options on futures;

     6.  Underwrite the distribution of securities of other issuers; however,
     the Fund may acquire "restricted" securities which, in the event of a
     resale, might be required to be

                                       24
<PAGE>
 
     registered under the Securities Act of 1933 on the ground that the Fund
     could be regarded as an underwriter as defined by that act with respect to
     such resale;

     7.  Purchase and sell real estate or interests in real estate, although it
     may invest in marketable securities of enterprises which invest in real
     estate or interests in real estate;

     8.  Purchase and sell commodities or commodity contracts, except that it
     may enter into (a) futures and options on futures and (b) foreign currency
     contracts;

     9.  Make margin purchases of securities, except for use of such short-term
     credits as are needed for clearance of transactions and except in
     connection with transactions in options, futures and options on futures;

     10.  Issue any senior security except to the extent permitted under the
     Investment Company Act of 1940.

Acorn Twenty and Acorn Foreign Forty

     In pursuing its investment objective each of Acorn Twenty and Acorn Foreign
Forty will not:

     1.  Acquire securities of any one issuer which at the time of investment
     (a) represent more than 10% of the voting securities of the issuer or (b)
     have a value greater than 10% of the value of the outstanding securities of
     the issuer;

     2.  With respect to 50% of the value of the Fund's total assets, purchase
     the securities of any issuer (other than cash items and U.S. government
     securities and securities of other investment companies) if such purchase
     would cause the Fund's holdings of that issuer to exceed 5% of the Fund's
     total assets;

     3.  Invest more than 25% of its total assets in a single issuer (other than
     U.S. government securities);

     4.  Invest more than 25% of its total assets in the securities of companies
     in a single industry (excluding U.S. government securities);

     5.  Make loans, but this restriction shall not prevent the Fund from (a)
     investing in debt securities, (b) investing in repurchase agreements, or
     (c) lending its portfolio securities, provided that it may not lend
     securities if, as a result, the aggregate value of all securities loaned
     would exceed 33% of its total assets (taken at market value at the time of
     such loan);

     6.  Borrow money except (a) from banks for temporary or emergency purposes
     in amounts not exceeding 33% of the value of the Fund's total assets at the
     time of borrowing, and (b) in connection with transactions in options,
     futures and options on futures;

                                       25
<PAGE>
 
     7.  Underwrite the distribution of securities of other issuers; however,
     the Fund may acquire "restricted" securities which, in the event of a
     resale, might be required to be registered under the Securities Act of 1933
     on the ground that the Fund could be regarded as an underwriter as defined
     by that act with respect to such resale;

     8.  Purchase and sell real estate or interests in real estate, although it
     may invest in marketable securities of enterprises which invest in real
     estate or interests in real estate;

     9.  Purchase and sell commodities or commodity contracts, except that it
     may enter into (a) futures and options on futures and (b) foreign currency
     contracts;

     10.  Make margin purchases of securities, except for use of such short-term
     credits as are needed for clearance of transactions and except in
     connection with transactions in options, futures and options on futures;

     11.  Issue any senior security except to the extent permitted under the
     Investment Company Act of 1940.

     The above restrictions (except the bracketed language) for each fund are
"fundamental," which means that they cannot be changed without the approval of
the lesser of (i) 67% of each fund's shares present at a meeting if more than
50% of the shares outstanding are present or (ii) more than 50% of each fund's
outstanding shares.

     In addition, Acorn Fund, Acorn International, Acorn USA, Acorn Twenty and
Acorn Foreign Forty are subject to a number of restrictions that may be changed
by the board of trustees without shareholder approval.  Under those non-
fundamental restrictions, the funds will not:

     a.  Acquire securities of other registered investment companies except in
     compliance with the Investment Company Act of 1940;

     b.  Invest more than 33% of its total assets (valued at time of investment)
     in securities of foreign issuers [this restriction applies only to Acorn
     Fund];

     c.  Invest more than 15% of its total assets in the securities of foreign
     issuers [this restriction applies only to Acorn Twenty].

     c.  Invest more than 10% of its total assets (valued at the time of
     investment) in securities of non-U.S. issuers, not including securities
     represented by American Depository Receipts [this restriction applies only
     to Acorn USA].

     e.  Invest more than 15% of its total assets in securities of United States
     issuers, under normal market conditions [this restriction applies only to
     Acorn Foreign Forty].

     d.  Invest in companies for the purpose of management or the exercise of
     control;

                                       26
<PAGE>
 
     e.  Pledge, mortgage or hypothecate its assets, except as may be necessary
     in connection with permitted borrowings or in connection with short sales,
     options, futures and options on futures;

     f.  Invest more than 10% of its total assets (valued at the time of
     investment) in restricted securities [this restriction applies only to
     Acorn Fund, Acorn International and Acorn USA];

     g.  Invest more than 15% of its net assets (valued at time of investment)
     in illiquid securities, including repurchase agreements in maturing in more
     than seven days; and

     h.  Make short sales of securities unless the Fund owns at least an equal
     amount of such securities, or owns securities that are convertible or
     exchangeable, without payment of further consideration, into at least an
     equal amount of such securities.

     Notwithstanding the foregoing investment restrictions, Acorn International,
Acorn USA, Acorn Twenty and Acorn Foreign Forty may purchase securities pursuant
to the exercise of subscription rights, provided that, in the case of Acorn
International and Acorn USA, such purchase will not result in either fund's
ceasing to be a diversified investment company.  Japanese and European
corporations frequently issue additional capital stock by means of subscription
rights offerings to existing shareholders at a price substantially below the
market price of the shares.  The failure to exercise such rights would result in
a fund's interest in the issuing company being diluted.  The market for such
rights is not well developed in all cases and, accordingly, a fund may not
always realize full value on the sale of rights.  The exception applies in cases
where the limits set forth in the investment restrictions would otherwise be
exceeded by exercising rights or would have already been exceeded as a result of
fluctuations in the market value of Acorn International's portfolio securities
with the result that the fund would be forced either to sell securities at a
time when it might not otherwise have done so, or to forego exercising its
rights.

                            Performance Information

     From time to time the funds may quote total return figures. "Total Return"
for a period is the percentage change in value during the period of an
investment in shares of a fund, including the value of shares acquired through
reinvestment of all dividends and capital gains distributions.  "Average Annual
Total Return" is the average annual compounded rate of change in value
represented by the Total Return for the period.

     Average Annual Total Return is computed as follows:

          ERV = P(1+T)/n/

     Where:  P = the amount of an assumed initial investment in shares of a fund
             T = average annual total return
             n = number of years from initial investment to the end of the
                 period
             ERV = ending redeemable value of shares held at the end of the
                 period

                                       27
<PAGE>
 
     For example, as of December 31, 1998 the Total Return and Average Total
Return on a $1,000 investment in each fund for the following periods were:

<TABLE>
<CAPTION>
ACORN FUND                     
- ----------                                              Average Annual 
                                       Total Return      Total Return
                                       ------------     --------------
<S>                                   <C>               <C>
 
1 year.............................            6.02%             6.02%
5 years............................           81.55%            12.67%
10 years...........................          352.81%            16.29%
Life of Fund (inception 6/10/70)...         7976.85%            16.61%

ACORN INTERNATIONAL                                                    
- -------------------                                     Average Annual 
                                       Total Return      Total Return
                                      --------------    --------------
 
1 year.............................           15.43%            15.43%
3 years............................           39.53%            11.74%
5 years............................           46.20%             7.89%
Life of Fund (inception 9/23/92)...          133.05%            14.45%
 
ACORN USA                                                             
- ---------                                               Average Annual 
                                       Total Return      Total Return
                                       -------------    --------------
1 Year.............................            5.79%             5.79%
Life of Fund (inception 9/4/96)....           63.05%            23.46%
 

ACORN TWENTY                                                          
- ------------                                            Average Annual 
                                       Total Return      Total Return
                                       -------------    --------------

Life of Fund (inception 11/23/98)              7.10%          N/A

 
ACORN FOREIGN FORTY                                     
- -------------------                         
                                                        Average Annual
                                       Total Return      Total Return
                                       --------------   --------------

Life of Fund (inception 11/23/98)             10.00%          N/A
</TABLE> 


     The funds impose no sales charges and pay no distribution expenses.  Income
taxes are not taken into account.  Performance figures quoted by the funds are
not necessarily indicative of future results.  Each fund's performance is a
function of conditions in the securities markets, portfolio management, and
operating expenses.  Although information about past performance is useful in
reviewing a fund's performance and in providing some basis for comparison with
other investment alternatives, it should not be used for comparison with other
investments using different reinvestment assumptions or time periods.

                                       28
<PAGE>
 
     The funds may note their mention or recognition in newsletters, newspapers,
magazines, or other media.  Portfolio managers and other members of WAM's staff
may make presentations at conferences or trade shows, appear on television or
radio programs, or conduct or participate in telephone conference calls, and the
Funds may announce those presentations, appearances or calls to some or all
shareholders, or to potential investors in the Funds.  Biographical and other
information about a Fund's portfolio manager, including information about awards
received by that portfolio manager or mentions of the manager in the media, may
also be described or quoted in Fund advertisements or sales literature.

     Ralph Wanger's book, A Zebra in Lion Country: Ralph Wanger's Investment
Survival Guide (Simon & Schuster, 1997) may be advertised from time to time, and
mention of the book may be made in fund sales literature. Mr. Wanger's book
describes the investment philosophies and techniques that have guided his
management of the Acorn funds over the last few decades. He has been portfolio
manager of Acorn Fund since it was founded by Irving Harris in 1970. On May 
22-23, 1999 only, copies of Mr. Wanger's book will be available free of charge
to attendees of the Los Angeles Times 3rd Annual Investment Strategies
Conference.

     In advertising and sales literature, each fund's performance may be
compared with those of market indexes and other mutual funds.  In addition to
the performance information described above, a fund might use comparative
performance as computed in a ranking or rating determined by Lipper Analytical
Services, Inc., an independent service that monitors the performance of over
1,000 mutual funds, Morningstar, Inc., or another service.

     The funds may also use statistics to indicate volatility or risk.  The
premise of each of these measures is that greater volatility connotes greater
risk undertaken in achieving performance. One measure of volatility is beta.
Beta is the volatility of a fund's total return relative to the movements of a
benchmark index.  A beta greater than one indicates volatility greater than the
index, and a beta of less than one indicates a volatility less than the index.
Another measure of volatility is R-squared.  It reflects the percentage of a
fund's price movements that are explained by movements in the benchmark index.
An R-squared of 1.00 indicates that all movements of a fund's price are
completely explained by movements in the index. Generally, a higher R-squared
will indicate a more reliable beta figure.  Alpha is a measure used to discuss a
fund's relative performance.  Alpha measures the actual return of a fund
compared to the expected return of a fund given its risk (as measured by beta).
The expected return of a fund is based on how historical movements of the
benchmark index and historical performance of a fund compare to the benchmark
index.  The expected return is computed by multiplying the advance or decline in
a market represented by a fund's beta.  A positive alpha quantifies the value
that a fund manager has added and a negative alpha quantifies the value that a
fund manager has lost.  Beta and R-squared are calculated by performing a least
squares linear regression using five years of monthly total return figures for
each portfolio and benchmark combination.  Alpha is calculated by taking the
difference between the average monthly portfolio return and the beta-adjusted
average monthly benchmark return.  The result of this calculation is then
geometrically annualized.

     The following are some benchmark indices utilized by the funds:  Salomon
Brothers Extended Market Index ("EMI"), an index of the bottom 20% of
institutionally investable capital of countries, selected by Salomon, excluding
the U.S.; Morgan Stanley's Europe, Australasia Far East Index ("EAFE"), an index
of companies throughout the world in proportion to world stock market
capitalizations, excluding the U.S. and Canada; the Standard & Poor's 500 Stock
Index ("S&P 500"), a broad, market-weighted average of U.S. blue-chip companies;
the Standard & Poor's MidCap 400 ("S&P 400"), also a broad, market-weighted
average of U.S. companies in the next tier down in size from the S&P 500; and
the Russell 2000 Index, an index formed by taking the largest 3,000 small
companies in the U.S. and eliminating the largest 1,000 of those

                                       29
<PAGE>
 
companies, leaving an unweighted index of 2000 small companies. All indexes are
unmanaged and include reinvested dividends.

     As of December 31, 1998, some statistics for the funds are as follows:

<TABLE>
<CAPTION>
                                         R2       Beta   Alpha
                                     ----------   ----   ------
     Acorn Fund
     ----------
<S>                                  <C>          <C>    <C>
               vs. S&P 500                 0.70   0.89   -6.90%
               vs. Russell 2000            0.82   0.79    5.74%
 
     Acorn International
    --------------------
               vs. EMI Ex U.S.             0.68   0.80    4.29%
               vs. EAFE                    0.63   0.70    1.58%
</TABLE>

     Other measures of volatility and relative performance may be used as
appropriate.  All such measures will fluctuate and do not represent future
results.

                              Investment Adviser

     Wanger Asset Management, L.P. ("WAM"), serves as the investment adviser for
the funds and for other institutional accounts.  As of the date of this SAI, WAM
has approximately $7 billion under management, including the funds.  WAM is a
limited partnership managed by its general partner, Wanger Asset Management,
Ltd. ("WAM Ltd."), whose stockholders are Ralph Wanger, Charles P. McQuaid, Leah
J. Zell, Marcel P. Houtzager, Robert A. Mohn, John H. Park. and Margaret M.
Forster.  Ralph Wanger is the president of WAM Ltd.  On matters submitted to the
shareholders of WAM Ltd., each shareholder has one vote (or a lesser vote in the
case of new shareholders).  With certain exceptions (including for extraordinary
transactions, for which Mr. Wanger's consent is required), decisions are made by
majority vote.  WAM commenced operations in 1992.

     WAM furnishes continuing investment supervision to the funds under an
investment advisory agreement (the "Agreement") and is responsible for overall
management of the funds' business affairs.  It furnishes office space, equipment
and personnel to the funds; it assumes substantially all expenses for
bookkeeping, and assumes the expenses of printing and distributing the funds'
prospectus and reports to prospective investors.  The Agreement will continue in
effect as to each fund through June 30, 1999, and thereafter from year to year
so long as its continuance as to each fund is approved at least annually by (i)
the board of trustees of Acorn or by the holders of a majority of that fund's
outstanding voting securities as defined by the Investment Company Act of 1940
and (ii) a majority of the members of Acorn's board of trustees who are not
otherwise affiliated with Acorn or WAM, cast in person at a meeting called for
that purpose.  Any amendment to the Agreement must be approved in the same
manner.  The Agreement may be terminated as to a fund without penalty by the
vote of the board of trustees of Acorn or the shareholders of that fund (by a
majority as defined in the 1940 Act) on sixty days' written notice to WAM or by
WAM on sixty days' notice to the fund, and will terminate

                                       30
<PAGE>
 
automatically in the event of its assignment. The fees payable by a fund under
the Agreement are the obligation only of that fund and impose no liability on
the other funds.

     The advisory fees the funds pay to WAM are calculated daily and paid
monthly, at the annual rates shown below:

     Acorn Fund

               Average Daily Net Assets            Rate of Fee
               ------------------------            -----------

               First $700 million                     0.75%
               $700 million to $2 billion             0.70%
               In excess of $2 billion                0.65%

     Acorn International

               Average Daily Net Assets            Rate of Fee
               ------------------------            -----------

               First $100 million                     1.20%
               $100 million to $500 million           0.95%
               In excess of $500 million              0.75%

     Acorn USA

               Average Daily Net Assets            Rate of Fee
               ------------------------            -----------

               First $200 million                     0.95%
               In excess of $200 million              0.90%

     Acorn Twenty

                                                   Rate of Fee
                                                   -----------

                                                      0.90%

     Acorn Foreign Forty

                                                   Rate of Fee
                                                   -----------

                                                      0.95%

                                       31
<PAGE>
 
     The advisory fees paid to WAM by each fund for the fiscal years ended
December 31. 1998, 1997 and 1996 were as follows:

<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------
        Fund                                      1998                           1997                           1996
- ------------------------------------------------------------------------------------------------------------------------
<S>                           <C>                            <C>                            <C>
Acorn Fund                                     $24,905,000                    $14,349,000                    $12,437,000
- ------------------------------------------------------------------------------------------------------------------------
Acorn International                            $14,124,000                    $16,235,000                    $13,255,000
- ------------------------------------------------------------------------------------------------------------------------
Acorn USA                                      $ 2,336,000                    $ 1,199,000                    $   101,000
- ------------------------------------------------------------------------------------------------------------------------
Acorn Twenty                                   $  26,000**                            ---                            ---
- ------------------------------------------------------------------------------------------------------------------------
Acorn Foreign Forty                            $  11,000**                            ---                            ---
- ------------------------------------------------------------------------------------------------------------------------
</TABLE>
     *From inception on September 4, 1996.
     **From inception on November 23, 1998.


     Acorn has a separate administrative services agreement with WAM under which
WAM receives a fee, calculated daily and paid monthly, at the annual rate of
0.05 of 1% of each fund's average daily net assets.  The funds pay the cost of
custodial, stock transfer, dividend disbursing, audit and legal services, and
membership in trade organizations.  They also pay other expenses such as the
cost of maintaining the registration of their shares under federal law,
complying with state securities laws, proxy solicitations, printing and
distributing notices and copies of the prospectus and shareholder reports
furnished to existing shareholders, taxes, insurance premiums and the fees of
trustees not affiliated with WAM.

                                  Distributor

     Shares of each fund are offered for sale by WAM Brokerage Services, L.L.C.
("WAM BD") without any sales commissions, 12b-1 fees or other charges to the
funds or their shareholders.  WAM BD is wholly-owned by WAM and WAM Ltd.  All
distribution expenses relating to the funds are paid by WAM, including the
payment or reimbursement of any expenses incurred by WAM BD.  The Distribution
Agreement for Acorn Fund, Acorn International and Acorn USA will continue in
effect through December 31, 1999 and thereafter from year to year provided such
continuance is approved annually (i) by a majority of the trustees or by a
majority of the outstanding voting securities of the Trust, and (ii) by a
majority of the trustees who are not parties to the Agreement or interested
persons of any such party. The Distribution Agreement for Acorn Twenty and Acorn
Foreign Forty will continue in effect through June 30, 1999 and thereafter from
year to year provided such continuance is approved annually (i) by a majority of
the trustees or by a majority of the outstanding voting securities of the Trust,
and (ii) by a majority of the trustees who are not parties to the Agreement or
interested persons of any such party.

     The Trust has agreed to pay all expenses in connection with registration of
its shares with the Securities and Exchange Commission and any auditing and
filing fees required in compliance with various state securities laws.  WAM
bears all sales and promotional expenses, including the cost of prospectuses and
other materials used for sales and promotional purposes by WAM BD.

                                       32
<PAGE>
 
WAM BD offers the funds' shares only on a best efforts basis. WAM BD is located
at 227 West Monroe Street, Suite 3000, Chicago, Illinois 60606.

                                   The Trust

     The Trust is a Massachusetts business trust organized under an Agreement
and Declaration of Trust dated April 21, 1992 (the "Declaration of Trust").  The
Declaration of Trust may be amended by a vote of either the Trust's shareholders
or its trustees.  The Trust may issue an unlimited number of shares, in one or
more series as the board of trustees may authorize.  Any such series of shares
may be further divided, without shareholder approval, into two or more classes
of shares having such preferences or special or relative rights or privileges as
the trustees may determine.  The shares of the funds are not currently divided
into classes.  Acorn Fund, Acorn International, Acorn USA, Acorn Twenty and
Acorn Foreign Forty are the only series of the Trust currently being offered.
The board of trustees may authorize the issuance of additional series if deemed
advisable, each with its own investment objective, policies and restrictions.
All shares issued will be fully paid and non-assessable and will have no
preemptive or conversion rights.

     Under Massachusetts law, the shareholders of the Trust may, under certain
circumstances believed to be remote, be held personally liable for the Trust's
obligations.  However, the Declaration of Trust disclaims liability of
shareholders and the Trust's trustees and officers for acts or obligations of
the Trust and requires that notice of such disclaimer be given in each
agreement, obligation or contract entered into or executed by the Trust or the
board of trustees.  The Declaration of Trust provides for indemnification out of
the assets of the Trust of all losses and expenses of any shareholder held
personally liable for the obligations of the Trust.  Thus, the risk of a
shareholder incurring financial loss on account of shareholder liability is
remote, since it is limited to circumstances in which the disclaimer is
inoperative and the Trust itself is unable to meet its obligations.

     On any matter submitted to a vote of shareholders, shares are voted in the
aggregate and not by individual series except that shares are voted by
individual series when required by the Investment Company Act of 1940 or other
applicable law, or when the board of trustees determines that the matter affects
only the interests of one series, in which case shareholders of the unaffected
series are not entitled to vote on such matters.  All shares of the Trust are
voted together in the election of trustees.

                                       33
<PAGE>
 
                             Trustees and Officers

     The board of trustees has overall responsibility for the Trust's and the
Funds' affairs.  The trustees and officers of the Trust, their dates of birth
and their principal business activities during the past five years are:

<TABLE>
<CAPTION>
Name and Date of         Position(s)         Principal Occupation(s) During Past Five Years
- ----------------         ----------          -----------------------------------------------
Birth                    Held with the 
- -----                    -------------
                         Trust  
                         -----

<C>                      <S>                 <C>
Irving B. Harris         Trustee and         Chairman of the executive committee and director, Pittway Corporation
8/4/1910                 chairman            (multi-product manufacturer and publisher); Chairman, William Harris
                                             Investors, Inc. (investment adviser); Chairman, The Harris Foundation
                                             (charitable foundation); Director, Teva Pharmaceutical Industries, Inc.
                                             (pharmaceutical manufacturer)
 
Ralph Wanger*            Trustee and         Trustee and President, Wanger Advisors Trust; Director, Wanger Investment
6/21/1934                President           Company plc; Principal, Wanger Asset Management, L.P.
 
James H. Lorie           Trustee and Vice    Eli B. and Harriet B. Williams Professor of Business Administration
2/23/1922                Chairman            Emeritus, University of Chicago Graduate School of Business; director,
                                             Thornburg Mortgage Asset Corp. (REIT) and Santa Fe Natural Tobacco
 
Leo A. Guthart           Trustee             Vice Chairman, Pittway Corporation (multi-product manufacturer and
9/26/1937                                    publisher); chief executive officer, Pittway Corporation's Security Group
                                             of Companies which include ADEMCO (manufacturer of alarm equipment), ADI
                                             (distributor of security equipment), Fire Burglary Instruments (supplier
                                             of security control panels), First Alert Professional (alarm dealers),
                                             Alarm Net (cellular radio service) and Cylink Corporation (supplier of
                                             encryption equipment)(chairman); director, AptarGroup, Inc. (producer of
                                             dispensing valves, pumps and closures); chairman of the board of trustees,
                                             Hofstra University; chairman, Tech Transfer Island Corp. (private
                                             investment partnership); director, Long Island Research Institute.
 
Jerome Kahn, Jr.         Trustee             President, William Harris Investors, Inc. (investment adviser); director,
4/13/1934                                    Pittway Corporation (multi-product manufacturer and publisher)
 
David C. Kleinman        Trustee             Senior lecturer in business administration, University of Chicago Graduate
10/12/1935                                   School of Business; business consultant;  Director, Irex Corporation
                                             (insulation contractor)
 
Charles P. McQuaid*      Trustee and         Trustee and Senior Vice President, Wanger Advisors Trust; Principal and
8/27/1953                Senior Vice         Director of Research, Wanger Asset Management, L.P.
                         President
</TABLE> 

                                       34
<PAGE>
 
<TABLE>
<CAPTION>
Name and Date of         Position(s)         Principal Occupation(s) During Past Five Years
- ----------------         ----------          -----------------------------------------------
Birth                    Held with the 
- -----                    -------------
                         Trust  
                         -----

<S>                      <C>                 <C>  
Roger S. Meier           Trustee             President, AMCO, Inc. (investment and real estate management); director,
1/18/1926                                    Fred Meyer, Inc. (retail chain); Director, Red Lion Inns Limited
                                             Partnership (hotel chain); Director and advisory board member, Key Bank of
                                             Oregon (banking); Chairman of Investment Council and member of Committee
                                             of Legacy Systems (hospital); Executive Director and Chairman of
                                             investment committee, Portland Art Museum
 
Allan B. Muchin          Trustee             Partner, Katten, Muchin & Zavis (law firm); Director, Alberto-Culver
1/10/1936                                    Company (toiletries).
 
Robert E. Nason          Trustee             Director, Hach Company (manufacturer and distributor of water testing and
7/29/1936                                    monitoring products and agents); Director, Fairfax Insurance Limited
                                             (privately owned insurance company); from 1990-1998, Executive Partner and
                                             chief executive officer, member of the executive committee and member of
                                             the policy board of Grant Thornton International (public accounting firm).
 
Katherine Schipper       Trustee             Eli B. and Harriet B. Williams Professor of Accounting, KPMG Peat Marwick
10/04/1949                                   Faculty Research Scholar and Director of the Institute of Professional
                                             Accounting, University of Chicago Graduate School of Business.
 
Margaret M. Forster      Vice President      Analyst and Portfolio Manager, Wanger Asset Management, L.P., since 1994;
1/28/1960                                    assistant professor of finance, Kellogg Graduate School of Management,
                                             Northwestern University, 1993-1994.
Marcel P. Houtzager      Vice President      Vice President, Wanger Advisors Trust; Principal, analyst and portfolio
10/26/1960                                   manager, Wanger Asset Management, L.P.
 
Kenneth A. Kalina        Assistant           Assistant Treasurer, Wanger Advisors Trust; Fund controller, Wanger Asset
8/4/1959                 Treasurer           Management, L.P., since September 1995; prior thereto, treasurer of the
                                             Stein Roe Mutual Funds.
 
Bruce H. Lauer           Vice President,     Vice President and treasurer, Wanger Advisors Trust; chief administrative
7/22/1957                Assistant           officer, Wanger Asset Management, L.P. since April 1995; director, Wanger
                         Secretary and       Investment Company plc; prior thereto, first vice president, investment
                         Treasurer           accounting, Kemper Financial Services, Inc.
 
Robert A. Mohn           Vice President      Vice President, Wanger Advisors Trust; principal, analyst and portfolio
9/13/1961                                    manager, Wanger Asset Management, L.P.
 
John H. Park             Vice President      Vice President, Wanger Advisors Trust; principal, analyst and portfolio
5/30/1967                                    manager, Wanger Asset Management. L.P. (since 1993); analyst.
 
Mark H. Yost             Vice President      Analyst and portfolio manager, Wanger Asset Management. L.P., since
6/28/1963                                    October 1995; co-portfolio manager, Wanger U.S. Smaller Companies Fund
                                             since June 2997; portfolio manager of WAM Yost Partnership, L.P.; prior
                                             thereto, investment analyst, First Chicago Corporation.
</TABLE> 

                                       35
<PAGE>
 
<TABLE>
<CAPTION>
Name and Date of         Position(s)         Principal Occupation(s) During Past Five Years
- ----------------         ----------          -----------------------------------------------
Birth                    Held with the 
- -----                    -------------
                         Trust  
                         -----

<S>                      <C>                 <C>  
Leah J. Zell             Vice President      Vice President, Wanger Advisors Trust; principal, analyst and portfolio
5/23/1949                                    manager, Wanger Asset Management, L.P.
</TABLE>

     *Messrs. McQuaid and Wanger are trustees who are interested persons of
Acorn as defined in the Investment Company Act of 1940, and of WAM.  Messrs.
Harris, Lorie, and Wanger are members, and Mr. McQuaid is an alternate member,
of the executive committee, which has authority during intervals between
meetings of the board of trustees to exercise the powers of the board, with
certain exceptions.  As of December 1, 1998, the trustees and officers of Acorn
as a group owned beneficially less than 1% of the outstanding shares of the
funds.

     Mr. Wanger and Ms. Zell are married to each other.

     At January 31, 1999, the State of Illinois Deferred Compensation Plan, 604
Stratton Office Building, Springfield, IL 62706, held 19,974,389 shares, and
Charles Schwab & Co., Inc., 101 Montgomery Street, San Francisco, CA 94104,
("Schwab") held 11,379,160 shares of Acorn Fund as owners of record, but not
beneficially (9.80% and 5.58% of the outstanding shares, respectively). Schwab
held 12,682,052 shares of Acorn International (15.40% of the outstanding shares)
as owner of record, but not beneficially.  Schwab held 2,323,554 shares, and
National Financial Services Corporation, P.O. Box 3098, Church Street Station,
New York, NY 10008, Donaldson Lufkin & Jenrette Securities Corp, P.O. Box 2052,
Jersey City, NJ 07303, and Firstcinco Reinvest, P.O. Box 640229, Cincinnati, OH
45264, held 1,304,791, 1,213,449 and 1,158,744 shares, of Acorn USA (12.39%,
6.96%, 6.47% and 6.18% of the outstanding shares, respectively) as owners of
record, but not beneficially.

     During 1998 the funds paid fees aggregating $302,000 to board members who
were not affiliated with WAM.  The following table sets forth the total
compensation, (including any amounts deferred, as described below) paid by the
Trust during the fiscal year ended December 31, 1998 to each of the trustees of
the Trust:

                                       36
<PAGE>
 
<TABLE>
<CAPTION>
                               Aggregate      Aggregate       Aggregate         Aggregate         Aggregate           Total
- -------------------------        Comp.          Comp.         Comp.from        Comp. from        Comp. from            Comp.
                              from Acorn      from Acorn      Acorn USA           Acorn             Acorn              from
Name of Trustee                  Fund             Int.                           Twenty+           Foreign             Fund    
                                                                                                    Forty+          Complex (5) 
- -------------------------------------------------------------------------------------------------------------------------------
<S>                         <C>               <C>          <C>               <C>               <C>               <C>
Irving B. Harris                60,800            27,500         2,700               0                0               $91,000    
Leo A. Guthart                  23,450            10,500         1,050               0                0               $35,000    
Jerome Kahn, Jr.                23,450            10,500         1,050               0                0               $35,000    
David C. Kleinman               23,450            10,500         1,050               0                0               $35,000    
James H. Lorie                  23,950            10,500         1,050               0                0               $35,500    
Charles P. McQuaid                   0                 0             0               0                0                     0    
Roger S. Meier                  23,450            10,500         1,050               0                0               $35,000    
Adolph Meyer, Jr.*              19,430             8,700           870               0                0               $29,000    
Allan B. Muchin**                1,452               650            65               0                0               $ 2,167    
Robert E. Nason**                1,452               650            65               0                0               $ 2,167    
Katherine Schipper**             1,452               650            65               0                0               $ 2,167    
Ralph Wanger                         0                 0             0               0                0                     0    
- --------------------------------------------------------------------------------------------------------------------------------
</TABLE>
     +   Since November 23, 1998.
     *   Served on the Board of the Trust until December 31, 1998.
     ** Elected to the Board of the Trust effective December 1, 1998.


     The officers and trustees affiliated with WAM serve without any
compensation from the Trust.  Acorn has adopted a deferred compensation plan
(the "Plan") for its non-interested trustees.  Under the Plan, the trustees who
are not "interested persons" of Acorn or WAM ("participating trustees") may
defer receipt of all or a portion of their compensation from the Trust in order
to defer payment of income taxes or for other reasons.  The deferred
compensation payable to a participating trustee is credited to a book reserve
account as of the business day such compensation would have been paid to such
trustee. The deferred compensation accrues income from the date of credit in an
amount equal to the amount that would have been earned had such deferred
compensation (and all income earned thereon) been invested and reinvested in
shares of one or more of the funds.  If a participating trustee retires, such
trustee may elect to receive payments under the plan in a lump sum or in equal
annual installments over a period of five years.  If a participating trustee
dies, any amount payable under the Plan will be paid to that trustee's
beneficiaries.  Each fund's obligation to make payments under the Plan is a
general obligation of that fund.  No fund is liable for any other fund's
obligations to make payments under the Plan.

                                       37
<PAGE>
 
                        Purchasing and Redeeming Shares

     Purchases and redemptions are discussed in the funds' prospectus under the
headings "Your Account  How to Buy Shares" and "Your Account  How to Sell
Shares."  All of that information is incorporated herein by reference.

     Acorn may from time to time authorize certain financial services companies,
broker-dealers or their designees ("authorized agents") to accept share purchase
and redemption orders on behalf of the funds.  Some of those authorized agents
may charge transaction fees for their services.  For purchase orders placed
through an authorized agent, a shareholder will pay the fund's NAV per share
(see "Purchasing and Redeeming Shares - Net Asset Value," below) next computed
after the receipt by the authorized agent of such purchase order, plus any
applicable transaction charge imposed by the agent.  For redemption orders
placed through an authorized agent, a shareholder will receive redemption
proceeds which reflect the NAV per share next computed after the receipt by the
authorized agent of the redemption order, less any redemption fees imposed by
the agent.

     In some instances, an authorized agent will not charge any transaction fees
directly to investors in a fund.  However, for accounting and shareholder
servicing services provided by such agent with respect to fund share accounts
held on behalf of its customers, the agent may charge a fee, generally a
percentage of the annual average value of those accounts.  WAM pays any such
fees.

Net Asset Value

     Share purchase and redemption orders will be priced at a fund's NAV next
computed after such orders are received and accepted by:  (i) Acorn's transfer
agent; (ii) a broker-dealer or other financial services company authorized by
Acorn to accept purchase and redemption orders on the fund's behalf; or (iii)
such authorized broker-dealer's designee.  Each fund's NAV is determined only on
days on which the New York Stock Exchange ("NYSE") is open for trading.  The
NYSE is regularly closed on Saturdays and Sundays and on New Year's Day, the
third Monday in January, the third Monday in February, Good Friday, the last
Monday in May, Independence Day, Labor Day, Thanksgiving, and Christmas.  If one
of those holidays falls on a Saturday or Sunday, the NYSE will be closed on the
preceding Friday or the following Monday, respectively.

     Computation of NAV (and the sale and redemption of fund shares) may be
suspended or postponed during any period when (a) trading on the NYSE is
restricted, as determined by the Securities and Exchange Commission, or that
exchange is closed for other than customary weekend and holiday closings, (b)
the Commission has by order permitted such suspension, or (c) an emergency, as
determined by the Commission, exists making disposal of portfolio securities or
valuation of the net assets of the funds not reasonably practicable.

     For purposes of computing the NAV of a fund share, a security traded on a
securities exchange, or in an over-the-counter market in which transaction
prices are reported, is valued at the last sale price at the time of valuation.
A security for which there is no reported sale on the

                                       38
<PAGE>
 
valuation date is valued at the mean of the latest bid and ask quotations or, if
there is no ask quotation, at the most recent bid quotation. Securities for
which quotations are not available, or for which the market quotation is
determined not to represent a fair value, and any other assets are valued at a
fair value as determined in good faith by the board of trustees. Money market
instruments having a maturity of 60 days or less from the valuation date are
valued on an amortized cost basis. All assets and liabilities initially
expressed in foreign currencies are converted into U.S. dollars at the mean of
the bid and offer prices of such currencies against U.S. dollars quoted by any
major bank or dealer. If such quotations are not available, the rate of exchange
will be determined in accordance with policies established in good faith by the
board of trustees.

     Trading in the foreign securities of the funds' portfolios may take place
in various foreign markets at certain times and on certain days (such as
Saturday) when the NYSE is not open for business and the funds do not calculate
their NAVs.  Conversely, trading in the funds' foreign securities may not occur
at times and on days when the NYSE is open.  Because of the different trading
hours in various foreign markets, the calculation of NAV does not take place
contemporaneously with the determinations of the prices of many of the funds'
foreign securities.  Those timing differences may have a significant effect on a
fund's NAV.

     Acorn has elected to be governed by Rule 18f-1 under the Investment Company
Act of 1940 pursuant to which it is obligated to redeem shares solely in cash up
to the lesser of $250,000 or 1% of the NAV of a fund during any 90-day period
for any one shareholder.  Redemptions in excess of the above amounts will
normally be paid in cash, but may be paid wholly or partly by a distribution in
kind of securities.  If a redemption is made in kind, the redeeming shareholder
would bear any transaction costs incurred in selling the securities received.

     Due to the relatively high cost of maintaining smaller accounts, Acorn
reserves the right to redeem shares in any account for their then-current value
(which will be promptly paid to the investor) if at any time the account value
falls below $1,000 because of share redemptions.  An investor will be notified
that the value of his account is less than that minimum and allowed at least 30
days to bring the value of the account up to at least $1,000 before the
redemption is processed.  The Agreement and Declaration of Trust also authorizes
Acorn to redeem shares under certain other circumstances as may be specified by
the board of trustees.

     WAM acts as a shareholder servicing agent for the Reich & Tang Money Funds
(the "Money Funds") in connection with an exchange plan between the Acorn funds
and the Money Funds (the "Switch Plan").  For its services it receives a fee at
the rate of 0.35% of the average annual net assets of each account in a Money
Fund established through the Switch Plan, pursuant to a 12b-1 plan adopted by
the Money Funds.

                          Additional Tax Information

     Each fund intends to continue to qualify to be taxed as a regulated
investment company under Subchapter M of the Internal Revenue Code (the "Code")
so as to avoid payment of

                                       39
<PAGE>
 
federal income tax on its capital gains and net investment income currently
distributed to its shareholders.

     At the time of your purchase, a fund's NAV may reflect undistributed
income, capital gains, or net unrealized appreciation of securities held by that
fund.  A subsequent distribution to you of such amounts, although constituting a
return of your investment, will be taxable either as a dividend or capital gain
distribution, whether received in cash or reinvested in additional shares.  For
federal income tax purposes, any distribution that is paid in January but that
was declared in the prior calendar year is deemed paid in the prior calendar
year.

     You will be subject to income tax at ordinary rates on income dividends and
distributions of net short-term capital gains.  The Internal Revenue Service
Restructuring and Reform Act of 1998 eliminated the requirement that capital
assets be held for more than 18 months in order to be taxed at the lowest rate
in effect under current law, and instead permits capital assets to be so taxed
if held for more than one year.  This change applies generally to sales
transactions which occur during taxable years ending after December 31, 1997.
You will be subject to income tax at ordinary rates on income dividends and
distributions of net short-term capital gain.  Distributions of net long-term
capital gains are taxable to you as long-term capital gains (currently taxed at
a maximum rate of 20%) regardless of the length of time you have held your
shares.  Long-term gains are those derived from securities held by the Fund for
more than one year.

     You will be advised annually as to the source of distributions for tax
purposes.  If you are not subject to tax on your income, you will not be
required to pay tax on these amounts.  If you realize a loss on the sale of fund
shares held for six months or less, your short-term loss is recharacterized as
long-term to the extent of any long-term capital gain distributions you have
received with respect to those shares.

     Under certain circumstances, Acorn may be required to withhold 31% federal
income tax ("backup withholding") from dividend, capital gain and redemption
payments to you.  Backup withholding may be required if:  (a) you fail to
furnish your social security or other tax identification number; (b) you fail to
certify that your social security or tax identification number is correct and
that you are not subject to backup withholding due to the underreporting of
certain income; or (c) the IRS informs Acorn that your tax identification number
is incorrect.

     These certifications are contained in the application that you complete
when you open your fund account.  Acorn must promptly pay the IRS all amounts
withheld.  Therefore, it is usually not possible for Acorn to reimburse you for
amounts withheld.  You may, however, claim the amount withheld as a credit on
your federal income tax return.

     Foreign currency gains and losses, including the portion of gain or loss on
the sale of debt securities attributable to foreign exchange rate fluctuations,
are taxable as ordinary income.  If the net effect of these transactions is a
gain, the income dividend paid by a fund will be increased; if the result is a
loss, the income dividend paid by a fund will be decreased.

     Dividends paid by Acorn International and Acorn Foreign Forty are not
eligible for the dividends-received deduction for corporate shareholders, if as
expected, none of that fund's

                                       40
<PAGE>
 
income consists of dividends paid by United States corporations. A portion of
the dividends paid by Acorn Fund, Acorn USA and Acorn Twenty is expected to be
eligible for the dividends-received deduction. Capital gain distributions paid
from the funds are never eligible for this deduction.

     Income received by the funds from sources within various foreign countries
will be subject to foreign income taxes withheld at the source.  Under the Code,
if more than 50% of the value of a fund's total assets at the close of its
taxable year comprises securities issued by foreign corporations, that fund may
file an election with the IRS to "pass through" to its shareholders the amount
of foreign income taxes paid by that fund.  Pursuant to this election,
shareholders will be required to: (i) include in gross income, even though not
actually received, their respective pro rata share of foreign taxes paid by the
fund; (ii) treat their pro rata share of foreign taxes as paid by them; and
(iii) either deduct their pro rata share of foreign taxes in computing their
taxable income, or use it as a foreign tax credit against U.S. income taxes (but
not both).  No deduction for foreign taxes may be claimed by a shareholder who
does not itemize deductions.

     Each of Acorn International and Acorn Foreign Forty intends to meet the
requirements of the Code to "pass through" to its shareholders foreign income
taxes paid, but there can be no assurance that it will be able to do so.  Each
shareholder will be notified within 60 days after the close of each taxable year
of Acorn International or Acorn Foreign Forty, if the foreign taxes paid by the
fund will "pass through" for that year, and, if so, the amount of each
shareholder's pro rata share (by country) of (i) the foreign taxes paid, and
(ii) the fund's gross income from foreign sources.  Shareholders who are not
liable for federal income taxes, including retirement plans qualified under
Section 401 of the Code, will not be affected by any such "pass through" of
foreign tax credits.  Acorn Fund, Acorn USA and Acorn Twenty do not expect to be
able to "pass through" foreign tax credits.

                       Taxation of Foreign Shareholders

     The Code provides that dividends from net income, which are deemed to
include for this purpose each shareholder's pro rata share of foreign taxes paid
by Acorn International and Acorn Foreign Forty (see discussion of "pass through"
of the foreign tax credit to U.S. shareholders), will be subject to U.S. tax.
For shareholders who are not engaged in a business in the U.S., this tax would
be imposed at the rate of 30% upon the gross amount of the dividend in the
absence of a tax treaty providing for a reduced rate or exemption from U.S.
taxation.  Distributions of net long-term capital gains are not subject to tax
unless the foreign shareholder is a nonresident alien individual who was
physically present in the U.S. during the tax year for more than 182 days.

                            Portfolio Transactions

     Portfolio transactions of the funds are placed with those securities
brokers and dealers that WAM believes will provide the best value in transaction
and research services for each fund, either in a particular transaction or over
a period of time.  Although some transactions involve only brokerage services,
many involve research services as well.

                                       41
<PAGE>
 
     In valuing brokerage services, WAM makes a judgment as to which brokers are
capable of providing the most favorable net price (not necessarily the lowest
commission) and the best execution in a particular transaction.  Best execution
connotes not only general competence and reliability of a broker, but specific
expertise and effort of a broker in overcoming the anticipated difficulties in
fulfilling the requirements of particular transactions, because the problems of
execution and the required skills and effort vary greatly among transactions.

     In valuing research services, WAM makes a judgment of the usefulness of
research and other information provided to WAM by a broker in managing each
fund's investment portfolio.  In some cases, the information, e.g., data or
recommendations concerning particular securities, relates to the specific
transaction placed with the broker, but for the greater part the research
consists of a wide variety of information concerning companies, industries,
investment strategy, and economic, financial, and political conditions and
prospects, useful to WAM in advising that fund.

     The reasonableness of brokerage commissions paid by the funds in relation
to transaction and research services received is evaluated by WAM's staff on an
ongoing basis.  The general level of brokerage charges and other aspects of each
fund's portfolio transactions are reviewed periodically by the board of trustees
and its committee on portfolio transactions.

     WAM is the principal source of information and advice to the funds, and is
responsible for making and initiating the execution of investment decisions by
the funds.  However, the board of trustees recognizes that it is important for
WAM, in performing its responsibilities to the funds, to continue to receive and
evaluate the broad spectrum of economic and financial information that many
securities brokers have customarily furnished in connection with brokerage
transactions, and that in compensating brokers for their services, it is in the
interest of the funds to take into account the value of the information received
for use in advising the funds.  The extent, if any, to which the obtaining of
such information may reduce WAM's expenses in providing management services to
the funds is not determinable.  In addition, the board of trustees understands
that other clients of WAM might benefit from the information obtained for the
funds, in the same manner that the funds might benefit from information obtained
by WAM in performing services to others.

     Transactions of the funds in the over-the-counter market and the third
market are executed with primary market makers acting as principal except where
it is believed that better prices and execution may be obtained otherwise.

                                       42
<PAGE>
 
     Brokerage commissions incurred by each fund during the last three fiscal
years, not including the gross underwriting spread on securities purchased in
underwritten public offerings, were as follows:

<TABLE>
<CAPTION>
 
    Fund                                                 1998                   1997                   1996
- ---------------------------------------------------------------------------------------------------------------
<S>                                          <C>                    <C>                    <C>
Acorn Fund                                             $2,766,000             $2,952,000             $3,440,000
Acorn International                                     4,111,000              5,350,000              3,929,000
Acorn USA                                                 305,000                216,000                 88,900*
Acorn Twenty                                               53,000**                  N/A                    N/A
Acorn Foreign Forty                                        41,000**                  N/A                    N/A
</TABLE>

     * From commencement of operations on September 4, 1996.
     ** From commencement of operations on November 23, 1998.


     During 1998, each fund paid brokerage commissions in connection with
portfolio transactions involving purchases and sales to brokers who furnished
investment research services to the funds, as follows:

<TABLE>
<CAPTION>
Fund                                           Brokerage Commissions                Purchases and Sales
- --------------------------------------------------------------------------------------------------------------
<S>                                      <C>                                  <C>
Acorn Fund                                           $1,268,000                        $448 million
- --------------------------------------------------------------------------------------------------------------
Acorn International                                  $3,619,000                        $1,019 million
- --------------------------------------------------------------------------------------------------------------
Acorn USA                                            $   80,000                          $37 million
- --------------------------------------------------------------------------------------------------------------
Acorn Twenty                                         $   22,000                           $9 million
- --------------------------------------------------------------------------------------------------------------
Acorn Foreign Forty                                  $   37,000                          $12 million
- --------------------------------------------------------------------------------------------------------------
</TABLE>

     The funds and WAM each have adopted a code of ethics that, among other
things, regulates the personal transactions in securities of certain officers,
directors, partners and employees of Acorn and WAM.  Although investment
decisions for the funds are made independently from those for other investment
advisory clients of WAM, it may develop that the same investment decision is
made for one or more of the funds and one or more other advisory clients.  If
any of the funds and other clients purchase or sell the same class of securities
on the same day, the transactions will be allocated as to amount and price in a
manner considered equitable to each.

                                   Custodian

     State Street Bank and Trust Company, P.O. Box 8502, Boston Massachusetts
02266-8502 ("State Street") is the custodian for the funds.  It is responsible
for holding all securities and cash of the funds, receiving and paying for
securities purchased, delivering against payment securities sold, receiving and
collecting income from investments, making all payments covering expenses of the
funds, and performing other administrative duties, all as directed by authorized

                                       43
<PAGE>
 
persons of the funds.  State Street does not exercise any supervisory function
in such matters as purchase and sale of portfolio securities, payment of
dividends, or payment of expenses of the funds.  The funds have authorized State
Street to deposit certain portfolio securities of the funds in central
depository systems as permitted under federal law.  The funds may invest in
obligations of State Street and may purchase or sell securities from or to State
Street.

                             Independent Auditors

     Ernst & Young LLP, Sears Tower, 233 South Wacker Drive, Chicago, Illinois
60606 audits and reports on the funds' annual financial statements, reviews
certain regulatory reports and the funds' tax returns, and performs other
professional accounting, auditing, tax, and advisory services when engaged to do
so by the funds.

                                       44
<PAGE>
 
                    Appendix - Description of Bond Ratings

     A rating of a rating service represents the service's opinion as to the
credit quality of the security being rated.  However, the ratings are general
and are not absolute standards of quality or guarantees as to the
creditworthiness of an issuer. Consequently, WAM believes that the quality of
debt securities in which the funds invest should be continuously reviewed.  A
rating is not a recommendation to purchase, sell or hold a security, because it
does not take into account market value or suitability for a particular
investor.  When a security has received a rating from more than one service,
each rating should be evaluated independently.  Ratings are based on current
information furnished by the issuer or obtained by the ratings services from
other sources which they consider reliable.  Ratings may be changed, suspended
or withdrawn as a result of changes in or unavailability of such information, or
for other reasons.

     The following is a description of the characteristics of ratings used by
Moody's Investors Service, Inc. ("Moody's") and Standard & Poor's Corporation
("S&P").

Moody's Ratings

     Aaa--Bonds rated Aaa are judged to be the best quality.  They carry the
smallest degree of investment risk and are generally referred to as "gilt-edge".
Interest payments are protected by a large or by an exceptionally stable margin
and principal is secure.  Although the various protective elements are likely to
change, such changes as can be visualized are most unlikely to impair the
fundamentally strong position of such bonds.

     Aa--Bonds rated Aa are judged to be high quality by all standards.
Together with the Aaa group they comprise what are generally known as high grade
bonds.  They are rated lower than the best bonds because margins of protection
may not be as large as in Aaa bonds or fluctuation of protective elements may be
of greater amplitude or there may be other elements present which make the long
term risk appear somewhat larger than in Aaa bonds.

     A--Bonds rated A possess many favorable investment attributes and are to be
considered as upper medium grade obligations.  Factors giving security to
principal and interest are considered adequate but elements may be present which
suggest a susceptibility to impairment sometime in the future.

     Baa--Bonds rated Baa are considered as medium grade obligations, i.e., they
are neither highly protected nor poorly secured.  Interest payments and
principal security appear adequate for the present but certain protective
elements may be lacking or may be characteristically unreliable over any great
length of time.  Such bonds lack outstanding investment characteristics and in
fact have speculative characteristics as well.

     Ba--Bonds rated Ba are judged to have speculative elements; their future
cannot be considered as well assured.  Often the protection of interest and
principal payments may be very moderate and thereby not well safeguarded during
both good and bad times over the future.  Uncertainty of position characterizes
bonds in this class.

                                       45
<PAGE>
 
     B--Bonds rated B generally lack characteristics of the desirable
investment.  Assurance of interest and principal payments or of maintenance of
other terms of the contract over any long period of time may be small.

     Caa--Bonds rated Caa are of poor standing.  Such bonds may be in default or
there may be present elements of danger with respect to principal or interest.

     Ca--Bonds rated Ca represent obligations which are speculative in a high
degree.  Such bonds are often in default or have other marked shortcomings.

S&P Ratings
     AAA--Bonds rated AAA have the highest rating.  Capacity to pay principal
and interest is extremely strong.

     AA--Bonds rated AA have a very strong capacity to pay principal and
interest and differ from AAA bonds only in small degree.

     A--Bonds rated A have a strong capacity to pay principal and interest,
although they are somewhat more susceptible to the adverse effects of changes in
circumstances and economic conditions than bonds in higher rated categories.

     BBB--Bonds rated BBB are regarded as having an adequate capacity to pay
principal and interest.  Whereas they normally exhibit protection parameters,
adverse economic conditions or changing circumstances are more likely to lead to
a weakened capacity to pay principal and interest for bonds in this capacity
than for bonds in higher rated categories.

     BB--B--CCC--CC--Bonds rated BB, B, CCC and CC are regarded, on balance, as
predominantly speculative with respect to the issuer's capacity to pay interest
and repay principal in accordance with the terms of the obligation.  BB
indicates the lowest degree of speculation among such bonds and CC the highest
degree of speculation.  Although such bonds will likely have some quality and
protective characteristics, these are outweighed by large uncertainties or major
risk exposures to adverse conditions.

                                       46
<PAGE>
 
                             FINANCIAL STATEMENTS

                                       
                                       Wanger Advisors Trust--1998 Annual Report
- --------------------------------------------------------------------------------
Wanger U.S. Small Cap                 Statement of Investments December 31, 1998
<TABLE> 
<CAPTION> 
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares
<S>                                                                   <C> 
              Common Stocks--93.0%
              Information--39.4%
- --------------------------------------------------------------------------------
              Broadcasting--2.1%
   250,600    Data Transmission Network (b)                           $7,236,075
              Data Services for Farmers

- --------------------------------------------------------------------------------
              Television Programming--5.3%

   222,000    Liberty Media Group,                                    10,225,875
              Tele-Communications (b)
              CATV & Satellite Dish Programming

   330,200    United Video Satellite Group (b)                         7,800,975
              CATV & Satellite Dish Programming
- --------------------------------------------------------------------------------
                                                                      18,026,850

- --------------------------------------------------------------------------------
              Telephone Services--5.1%

   577,600    RCN Corporation (b)                                     10,216,300
              Metro Market: Voice, Video & Data Services

   193,300    Commonwealth Telephone (b)                               6,475,550
              Rural Market: Local, Long Distance
              & Internet Access

    68,600    Startec Global Communications (b)                          660,275
              International Telecommunications
- --------------------------------------------------------------------------------
                                                                      17,352,125

- --------------------------------------------------------------------------------
              Mobile Communications--6.6%

   411,000    Centennial Cellular (b)                                 16,851,000
              Cellular Franchises

   234,500    COMARCO (b)                                              5,628,000
              Wireless Network Testing
- --------------------------------------------------------------------------------
                                                                      22,479,000

- --------------------------------------------------------------------------------
              Telecommunications Equipment--2.2%

   425,900    Aspect Telecommunications (b)                            7,346,775
              Call Center Equipment

- --------------------------------------------------------------------------------
              Instrument--0.7%

    85,000    Mettler Toledo (b)                                       2,385,314
              Laboratory Products

- --------------------------------------------------------------------------------
              Business Software--1.5%

   314,000    JDA Software                                             3,041,875
              Software & Services for Retailers

   137,600    Systems & Computer Technology (b)                        1,892,000
              Enterprise Software & Services
- --------------------------------------------------------------------------------
                                                                       4,933,875

- --------------------------------------------------------------------------------
              Business Information and
              Marketing Services--1.1%

   353,400    Intelligent Information (b)                              2,385,450
              Technology Market Research

   178,100    InfoUSA, C1. B                                             935,025

   116,000    InfoUSA, C1. A                                             565,500
              Business Data for Sales Leads
- --------------------------------------------------------------------------------
                                                                       3,885,975

- --------------------------------------------------------------------------------
              Transaction Processors--3.6%

   247,300    National Data                                           12,040,418
              Credit Card & Health Claims Processor

- --------------------------------------------------------------------------------
              Computer Hardware & Related Systems--8.0%

   417,100    Micros Systems (b)                                      13,712,164
              Information Systems for Restaurants & Hotels

   300,600    Kronos (b)                                              13,320,337
              Time Accounting Software & Clocks

- --------------------------------------------------------------------------------
                                                                      27,032,501

- --------------------------------------------------------------------------------
              Gaming Equipment--0.8%

   113,000    International Game Technology                            2,747,315
              Slot Machines & Progressive Jackpots

- --------------------------------------------------------------------------------
              Computer Services--2.4%

   222,900    Sykes Enterprises (b)                                    6,798,450
              Call Center Services

   344,000    Aztec Technology Partners (b)                            1,247,000
              Technology Staffing Services

- --------------------------------------------------------------------------------
                                                                       8,045,450

- --------------------------------------------------------------------------------
              Information--Total                                     133,511,673
</TABLE> 

See accompanying notes to financial statements.

                                      47
<PAGE>

                                        Wanger Advisors Trust 1998 Annual Report
- --------------------------------------------------------------------------------
Wanger U.S. Small Cap                 Statement of Investments December 31, 1998

<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares
<S>                                                                   <C>
              Health Care--9.7%
- --------------------------------------------------------------------------------
              Biotechnology/Drug Delivery--0.5%

   117,000    Synaptic Pharmaceuticals (b)                            $1,755,000
              Receptor Targeted Drug Design

- --------------------------------------------------------------------------------
              Health Care Services--9.2%

   506,800    Lincare Holdings (b)                                    20,557,075
              Home Health Care Services

   475,000    First Health (b)                                         7,867,187
              PPO Network

   321,500    Magellan Health Services (b)                             2,692,563
              Mental Health Services

- --------------------------------------------------------------------------------
                                                                      31,116,825

- --------------------------------------------------------------------------------
              Health Care--Total                                      32,871,825

              Consumer Goods/Services--2.7%
- --------------------------------------------------------------------------------
              Retail--2.5%

   809,000    Host Marriott Services (b)                               8,393,375
              Fast Food Kiosks in Airports

- --------------------------------------------------------------------------------
              Casinos--0.2%

   115,200    Monarch Casino & Resort (b)                                604,800
              Casino/Hotel in Reno

- --------------------------------------------------------------------------------
              Consumer Goods/Services--Total                           8,998,175

              Finance--14.0%
- --------------------------------------------------------------------------------
              Banks/Savings & Loans--2.8%

   111,500    Washington Mutual                                        4,257,906
              West Coast Savings & Loan

    90,000    Texas Regional Bancshares                                2,255,625
              TexMex Bank

    67,500    Peoples Bank Bridgeport                                  1,864,687
              Mortgage & Credit Card Lender

   157,500    Coast Contingency Rights (b)                             1,043,439
              Litigation Claim Against US Government

- --------------------------------------------------------------------------------
                                                                       9,421,657

- --------------------------------------------------------------------------------
              Finance Companies--0.7%

   232,000    World Acceptance (b)                                     1,508,000
              Personal Loans

    70,000    Americredit                                                966,875
              Auto Lending

- --------------------------------------------------------------------------------
                                                                       2,474,875

- --------------------------------------------------------------------------------
              Insurance--7.8%

   348,600    UICI (b)                                                 8,540,700
              Health Insurance

   403,900    Acceptance Insurance (b)                                 8,178,975
              Crop Insurance

    21,000    Markel (b)                                               3,801,000
              Property & Casualty Insurance

   135,000    AmerUs Life Holdings                                     3,020,625
              Annuities/Life Insurance

    92,000    Leucadia National                                        2,898,000
              Insurance Holding Company

- --------------------------------------------------------------------------------
                                                                      26,439,300

- --------------------------------------------------------------------------------
              Money Management--2.7%

    66,000    SEI Investments                                          6,558,750
              Mutual Fund Administration

   167,817    Baker Fentress                                           2,569,697
              Closed-End Investment Company

- --------------------------------------------------------------------------------
                                                                       9,128,447

- --------------------------------------------------------------------------------
              Finance--Total                                          47,464,279
</TABLE>

See accompanying notes to financial statements.

                                      48
<PAGE>


                                        Wanger Advisors Trust 1998 Annual Report
- --------------------------------------------------------------------------------
Wanger U.S. Small Cap                 Statement of Investments December 31, 1998

<TABLE> 
<CAPTION> 
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares
<S>                                                                  <C>       
              Industrial Goods/Services--8.5%
- --------------------------------------------------------------------------------
              Machinery--1.3%

   270,700    Farr (b)                                                $2,740,837
              Filters

    91,000    Vallen (b)                                               1,820,000
              Safety Products Distribution

- --------------------------------------------------------------------------------
                                                                       4,560,837

- --------------------------------------------------------------------------------
              Steel--1.2%

   232,400    Atchison Casting (b)                                     2,149,700
              Steel Foundries

   126,400    Schnitzer Steel                                          1,817,000
              Scrap Steel Processor

- --------------------------------------------------------------------------------
                                                                       3,966,700

- --------------------------------------------------------------------------------
              Specialty Chemicals--1.1%
 
   189,600    Lilly Industries, Cl. A                                  3,780,150
              Industrial Coatings

- --------------------------------------------------------------------------------
              Other Industrial Services--4.9%
 
   476,200    Wackenhut, Cl. B                                        10,446,637
              Prison Management
 
   398,700    Insurance Auto Auctions (b)                              4,734,562
              Auto Salvage Services
 
   140,900    Compass International Services (b)                       1,497,062
              Collection Agencies

- --------------------------------------------------------------------------------
                                                                      16,678,261

- --------------------------------------------------------------------------------
              Industrial Goods/Services--Total                        28,985,948

              Energy/Minerals--15.9%
- --------------------------------------------------------------------------------
              Independent Power--7.6%

   689,600    CalEnergy (b)                                           23,920,500
              Power Plants/Competitive Utility

    38,000    AES Corporation (b)                                      1,800,250
              Power Plants

- --------------------------------------------------------------------------------
                                                                      25,720,750

- --------------------------------------------------------------------------------
              Oil/Gas Producers--2.5%

   698,900    Tesoro Petroleum (b)                                     8,474,163
              Oil Refinery/Gas Reserves

   139,000    Tipperary (b)                                              147,687
              Oil & Gas Producer

- --------------------------------------------------------------------------------
                                                                       8,621,850

- --------------------------------------------------------------------------------
              Oil Refining/Marketing/Distribution--4.5%

   258,000    Atmos Energy                                             8,320,500
              Natural Gas Utility

   137,000    Equitable Resources                                      3,990,125
              Natural Gas Utility & Producer
 
   279,100    Dynegy                                                   3,052,656
              Natural Gas Processing/Marketing

- --------------------------------------------------------------------------------
                                                                      15,363,281

- --------------------------------------------------------------------------------
              Oil Services--1.3%

    93,000    J Ray McDermott (b)                                      2,272,687
              Offshore Construction Company

   198,000    GeoScience (b)                                           2,165,625
              Offshore Seismic Equipment

- --------------------------------------------------------------------------------
                                                                       4,438,312

- --------------------------------------------------------------------------------
              Energy/Minerals--Total                                  54,144,193
</TABLE>

See accompanying notes to financial statements.

                                      49
<PAGE>


                                        Wanger Advisors Trust 1998 Annual Report
- --------------------------------------------------------------------------------
Wanger U.S. Small Cap                 Statement of Investments December 31, 1998

<TABLE> 
<CAPTION> 
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares or Principal
Amount
<S>                                                                <C>       
              Other Industries--2.8%                               
- --------------------------------------------------------------------------------
              Real Estate--1.8%                                    
                                                                   
    125,600   Forest City Enterprises Cl. A                          $3,297,000
              Shopping Centers                                     
                                                                   
     64,900   Gaylord Entertainment (b)                               1,955,112
              Opryland Hotel & Other Assets                        
                                                                   
     45,000   Cornerstone Properties                                    703,125
              Downtown Office Buildings                            
                                                                   
- --------------------------------------------------------------------------------
                                                                      5,955,237
                                                                   
- --------------------------------------------------------------------------------
              Transportation--1.0%                                 
                                                                   
    174,000   Hub Group (b)                                           3,371,250
              Freight Forwarder                                    
                                                                   
     66,000   Trailer Bridge (b)                                        101,062
              Tug & Barge Transportation                           
                                                                   
- --------------------------------------------------------------------------------
                                                                      3,472,312
                                                                   
- --------------------------------------------------------------------------------
              Other Industries--Total                                 9,427,549
                                                                   
Total Common Stocks--93.0%                                          315,403,642
- --------------------------------------------------------------------------------
(Cost: $265,298,784)                                               
                                                                   
- --------------------------------------------------------------------------------
Short-Term Obligations--7.6%                                       
                                                                   
$13,412,000   Ford Motor Credit 5.21% Maturing 01/04/99              13,406,177
                                                                   
$12,469,000   State Street Bank Repurchase Agreement                 12,469,000
              4.25% Maturing 01/04/99; 12/31/98 Agreement          
              Collateralized by U.S. Treasury Notes                
- --------------------------------------------------------------------------------
              (Amortized Cost: $25,875,177)                          25,875,177
                                                                   
- --------------------------------------------------------------------------------
Total Investments--100.6%                                           341,278,819
                                                                   
              (Cost: $291,173,961)                                 
                                                                   
Cash and Other Assets Less Liabilities--(0.6%)                       (2,159,938)
- --------------------------------------------------------------------------------
 
Total Net Assets--100%                                             $339,118,881
================================================================================
</TABLE>

     Notes to Statement of Investments:
 
(a)  At December 31, 1998, for federal income tax purposes cost of investments
     was $291,578,447 and net unrealized appreciation was $49,700,372 consisting
     of gross unrealized appreciation of $79,338,202 and gross unrealized
     depreciation of $29,637,830.

(b)  Non-income producing security.

See accompanying notes to financial statements.
 
                                      50
<PAGE>
 
                                       Wanger Advisors Trust--1998 Annual Report
- --------------------------------------------------------------------------------
Wanger International Small Cap        Statement of Investments December 31, 1998

<TABLE> 
<CAPTION> 
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares 
<S>                                                                     <C> 
              Common Stocks--96.6%

              Europe--66.0%
- --------------------------------------------------------------------------------
              Germany/Austria--3.1%

    34,000    Rhoen Klinikum                                         $ 3,378,362
              Hospital Management

   160,000    Scala Business Solutions                                 1,037,684
              GIC Units (b)
              ERP Software (Austria)
- --------------------------------------------------------------------------------
                                                                       4,416,046

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

              Denmark--1.1%

    20,000    Vest Wood                                                1,602,639
              Furniture

- --------------------------------------------------------------------------------
              Netherlands--5.9%
 
    92,000    Hunter Douglas                                           3,049,182
              Decorative Window Coverings
 
    44,000    Kempen                                                   2,339,851
              Stock Brokerage/Investment Management

   100,000    Unique International                                     2,291,255
              Human Resources

    26,051    Computer Service Solutions (b)                             617,720
              Computer Services
- --------------------------------------------------------------------------------
                                                                       8,298,008
 
- --------------------------------------------------------------------------------
              Finland--7.5%
 
   248,800    Talentum                                                 4,176,640
              Trade Journals & Multimedia

    90,000    Tieto, Cl. B                                             4,034,838
              Computer Services/Consulting
 
   150,000    Elcoteq Network                                          1,629,339
              Electrical Components
 
    70,000    Rapala Normark (b)                                         608,286
              Fishing & Hunting Equipment
 
     1,550    Spar Finland                                                67,346
              Grocery/Convenience Stores
- --------------------------------------------------------------------------------
                                                                      10,516,449

- --------------------------------------------------------------------------------
              Norway--0.3%

   149,800    P4 Radio Hele Norge                                        462,042
              Commercial Radio Station

     7,490    Electric Farm (b)                                            1,970
              Internet Services
- --------------------------------------------------------------------------------
                                                                         464,012

- --------------------------------------------------------------------------------
              Sweden--6.6%
 
   125,000    Elanders                                                 2,344,000
              Printer

   230,800    Semcon                                                   1,907,720
              Technical Consulting
 
   125,000    Caran                                                    1,542,105
              Engineering Consulting
 
   300,000    Micronic Laser Systems (b)                               1,406,400
              Electronics Production Equipment
 
   175,000    Mandator                                                 1,370,931
              Computer Services/Consulting

   350,000    Gylling Optima Class Q (b)                                 410,200

   325,000    Gylling Optima Class B (b)                                 400,947
              Batteries
- --------------------------------------------------------------------------------
                                                                       9,382,303

- --------------------------------------------------------------------------------
              France--2.7%

    15,000    Fininfo                                                  2,658,336
              Financial Data Feeds

    14,919    Cie des Signaux                                          1,094,985
              Computer Services/Telecom Equipment
- --------------------------------------------------------------------------------
                                                                       3,753,321

- --------------------------------------------------------------------------------
              United Kingdom--20.2%
 
   350,000    Seton Scholl Healthcare Group                            4,877,011
              Pharmaceuticals
 
   400,000    Parity                                                   3,810,100
              IT Staffing & Services
 
    60,000    NTL (b)                                                  3,386,250
              Voice, Video & Data Services
</TABLE> 

See accompanying notes to financial statements.

                                      51
<PAGE>
 
                                       Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Wanger International Small Cap       Statement of Investments  December 31, 1998

<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares
<S>           <C>                                                     <C>
 
              United Kingdom--cont.
- --------------------------------------------------------------------------------
 1,000,000    Workplace Technologies                                  $3,277,685
              Network Integration
 
   600,000    Informa Group                                            2,840,105
              Trade Journals & Conferences
 
 2,000,000    Electronics Boutique                                     2,687,036
              Videogame/Computer Software Stores
 
 1,500,000    Taylor Nelson                                            1,896,731
              Market Research
 
   500,000    Hogg Robinson                                            1,717,875
              Corporate Travel Management

    58,600    Euro Money Publications                                  1,364,981
              Financial Publications

   400,000    Oriflame International                                   1,141,366
              Cosmetics Sold Door-to-Door

    50,600    Vosper Thornycroft                                         646,986
              Naval Shipbuilding
 
   129,000    Edinburgh Fund Managers                                    531,210
              Investment Management

   350,000    Dialog (b)                                                 337,751
              Online Business Information
- --------------------------------------------------------------------------------
                                                                      28,515,087
 
- --------------------------------------------------------------------------------
              Spain/Portugal--6.3%
 
   100,000    Mapfre Vida                                              3,768,645
              Life Insurance/Mutual Funds
 
   250,000    Prosegur                                                 2,919,991
              Security Guards
                                                   
   100,000    Filmes Lusomundo (b)                                     1,254,012
              Newspapers, Radio, Video,
              Film Distribution (Portugal)
 
    18,200    Jeronimo Martins                                           995,642
              Hypermarkets/Supermarkets (Portugal)
- --------------------------------------------------------------------------------
                                                                       8,938,290

- --------------------------------------------------------------------------------
              Switzerland--4.7%

     4,000    Phoenix Mecano                                           2,402,621
              Electrical Components
 
     1,500    Pargesa                                                  2,369,860
              Industrial & Media Conglomerate
 
     3,000    Affichage                                                1,170,731
              Billboard Advertising
 
     2,600    Hiestand                                                   681,470
              Bakery
- --------------------------------------------------------------------------------
                                                                       6,624,682

- --------------------------------------------------------------------------------
              Italy/Greece--7.6%
 
   600,000    Autogrill                                                4,832,190
              Tollway Restaurants

   150,000    Banca Pop Commercia e Industria                          3,015,570
              Regional Bank

   150,000    Athens Medical Center                                    2,943,224
              Hospitals (Greece)
- --------------------------------------------------------------------------------
                                                                      10,790,984

- --------------------------------------------------------------------------------
              Europe--Total                                           93,301,821


              Asia--19.6%
- --------------------------------------------------------------------------------
              Hong Kong--2.9%

 1,640,000    Li and Fung                                              3,397,570
              Sourcing of Consumer Goods

   950,000    Dickson Concepts                                           735,740
              Luxury Goods Retailer
- --------------------------------------------------------------------------------
                                                                       4,133,310
</TABLE> 
See accompanying notes to financial statements.

                                       52
<PAGE>
 
                                       Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Wanger International Small Cap        Statement of Investments December 31,1998

<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------
Number of                                                                  Value
Shares
<S>                                                                   <C>  
 
              Japan--6.8%

    90,000    NuSkin Enterprises (b)                                  $2,126,250
              Cosmetics Sold Door-to-Door

    60,000    Enix Corporation                                         1,962,765
              Game Software Developer
 
    13,800    Ryohin Keikaku                                           1,841,223
              Specialty Consumer Goods Retailer

    75,000    Kawasumi Labs                                            1,476,065
              Medical Supplies
 
    75,700    Shinki                                                     932,830
              Loans to Consumers and Small Businesses
 
    16,000    Nichii Gakkan                                              666,666
              Hospital Administrative Services
 
    12,500    Hokuto                                                     304,742
              Mushroom Grower
 
    49,500    Tecmo                                                      302,792
              Game Software Developer
- --------------------------------------------------------------------------------
                                                                       9,613,333

- --------------------------------------------------------------------------------
              Malaysia--0.2%

   388,000    Computer Systems Advisor                                   270,100
              Systems Integration & Software Services

- --------------------------------------------------------------------------------
              Singapore--9.7%

 1,037,000    Venture Manufacturing                                    3,959,454
              Electronic Manufacturing Services
 
 1,700,400    Star Cruises (b)                                         3,587,844
              Cruise Line
 
 8,000,000    Omni Industries                                          2,569,696
              Electronic Manufacturing Services
 
   800,000    Datacraft Asia                                           1,416,000
              Network Systems Integration

 4,233,000    Datapulse Technology (b)                                 1,192,936
              CD-ROM Replication

   350,000    Natsteel Electronics                                       890,909
              Electronic Manufacturing Services
- --------------------------------------------------------------------------------
                                                                      13,616,839

- --------------------------------------------------------------------------------
              Asia--Total                                             27,633,582


              Latin America--4.3%
- --------------------------------------------------------------------------------
              Mexico--3.2%
 
   800,000    Grupo Continental                                        1,937,310
              Coca-Cola Bottler
 
   641,000    Corp Interamericana                                      1,749,950
              de Entretenimiento (b)
              Special Events & Live Entertainment
 
 1,240,000    Nadro, Series L                                            789,888
              Pharmaceutical Distribution
- --------------------------------------------------------------------------------
                                                                       4,477,148

- --------------------------------------------------------------------------------
              Brazil--1.1%

   150,000    Elevadores Atlas                                         1,613,837
              Elevator Services

- --------------------------------------------------------------------------------
              Latin America--Total                                     6,090,985

              Other Countries--6.7%
- --------------------------------------------------------------------------------
              Australia--1.6%

 1,128,352    Tyndall Australia                                        1,730,329
              Money Management & Insurance

   362,965    Anaconda Nickel (b)                                        556,606
              Nickel Mining
- --------------------------------------------------------------------------------
                                                                       2,286,935
</TABLE> 

See accompanying notes to financial statements.

                                       53
<PAGE>
 
                                       Wanger Advisors Trust--1998 Annual Report
- --------------------------------------------------------------------------------
Wanger International Small Cap        Statement of Investments  December 31,1998

<TABLE>
<CAPTION>


Number of                                                                  Value
Shares or 
Principal
Amount
<S>                                                                     <C> 

- --------------------------------------------------------------------------------
              Canada--3.9%

   270,000    LGS Group (b)                                           $2,021,485
              Computer Systems Integration

   100,000    MDSI Mobil Data Solutions (b)                            1,787,500
              Wireless Software
 
   122,900    Shaw Industries                                          1,000,165
              Oil Field Services

    50,000    Architel Systems (b)                                       651,041
              Software for Telecommunications
- --------------------------------------------------------------------------------
                                                                       5,460,191

- --------------------------------------------------------------------------------
              Israel--0.6%

    30,000    Galileo Technology (b)                                     810,000
              Semiconductors

- --------------------------------------------------------------------------------
              South Africa--0.6%

   552,700    Energy Africa (b)                                          845,566
              Oil & Gas Producer

- --------------------------------------------------------------------------------
              Other--Total                                             9,402,692


Total Common Stocks--96.6%                                           136,429,080
- --------------------------------------------------------------------------------
              (Cost:  $109,875,402)


Short-Term Obligation--3.3%                                            4,723,000
- --------------------------------------------------------------------------------

$4,723,000    State Street Bank Repurchase Agreement
              3.25% 01/04/99; 12/31/98 Agreement
              Collateralized by U.S. Treasury Notes
              (Cost:  $4,723,000)

Total Investments--99.9%                                             141,152,080
- --------------------------------------------------------------------------------
              (Cost:  $ 114,598,402)

Cash and Other Assets Less Liabilities--0.1%                             101,229
- --------------------------------------------------------------------------------

Total Net Assets--100%                                              $141,253,309
================================================================================
</TABLE> 
     Notes to Statement of Investments:


(a)  At December 31, 1998, for federal income tax purposes cost of investments
     was $114,696,573 and net unrealized appreciation was $26,455,507 consisting
     of gross unrealized appreciation of $37,317,390 and gross unrealized
     depreciation of $10,861,883.

(b)  Non-income producing security.

See accompanying notes to financial statements.

                                       54
<PAGE>
 
                                     Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Wanger International Small Cap       Portfolio Diversification December 31, 1998

At December 31, 1998 the Fund's portfolio of investments 
as a percentage of net assets was diversified as follows:

<TABLE>
<CAPTION>
                                                 Value    Percent
- -----------------------------------------------------------------
<S>                                       <C>             <C>
Information
Computer Services                         $ 19,821,559      14.0%
Publishing                                   9,139,634       6.5
Contract Manufacturing                       8,612,997       6.1
Business Information &                                
  Marketing Services                         4,892,818       3.5
Business Software                            4,528,832       3.2
CATV                                         3,386,250       2.4
Semiconductors & Related Equipment           2,216,400       1.6
Gaming Equipment                             1,962,766       1.4
Domestic Consumer Software                   1,787,500       1.3
Advertising                                  1,170,732       0.8
Radio                                          464,008       0.3
- -----------------------------------------------------------------
                                            57,983,496      41.1
                                                      
- -----------------------------------------------------------------
Health Care                                           
Hospital Management                          6,321,587       4.5
Pharmaceuticals                              4,877,012       3.5
Hospital/Laboratory Supplies                 1,476,064       1.0
Health Care Services                           666,667       0.5
- -----------------------------------------------------------------
                                            13,341,330       9.5
                                                      
- -----------------------------------------------------------------
Consumer Goods/Services                               
Retail                                       6,259,642       4.4
Travel                                       5,305,717       3.8
Restaurants                                  4,832,189       3.4
Nondurables                                  3,267,616       2.3
Beverages                                    1,937,310       1.4
Furniture/Textile                            1,602,640       1.2
Food                                           986,214       0.7
Consumer Goods Distribution                    857,235       0.6
Leisure Products                               608,287       0.4
International Consumer Software                302,793       0.2
Other Durable Goods                          3,860,330       2.7
Other Entertainment                          1,749,949       1.2
- -----------------------------------------------------------------
                                            31,569,922      22.3
                                                      
- -----------------------------------------------------------------
Finance                                               
Insurance                                    3,768,642       2.6
Banks                                        3,015,570       2.1
Closed-End Funds                             2,369,858       1.7
Brokerage                                    2,339,852       1.7
Money Management                             2,261,537       1.6
Finance Companies                              932,828       0.7
- -----------------------------------------------------------------
                                            14,688,287      10.4
                                                      
- -----------------------------------------------------------------
Industrial Goods/Services                             
Outsourcing and Training Services           10,150,924       7.2
Electrical Components                        4,031,961       2.8
Other Industrial Services                    1,613,838       1.1
Machinery                                      646,985       0.5
- -----------------------------------------------------------------
                                            16,443,708      11.6
                                                      
- -----------------------------------------------------------------
Energy/Minerals                                       
Oil Services                                 1,000,163       0.7
Oil/Gas Producers                              845,567       0.6
Non-Ferrous Metals                             556,607       0.4
- -----------------------------------------------------------------
                                             2,402,337       1.7
                                                      
- -----------------------------------------------------------------
Total Common Stocks                        136,429,080      96.6
                                                      
Short-Term Obligations                       4,723,000       3.3
- -----------------------------------------------------------------
                                                      
Cash and Other Assets Less Liabilities         101,229       0.1
- -----------------------------------------------------------------
                                                      
Net Assets                                $141,253,309     100.0%
- -----------------------------------------------------------------
</TABLE>

See accompanying notes to financial statements.

                                      55
<PAGE>
 
<TABLE>
<CAPTION>


                                                       Wanger Advisors Trust 1998 Annual Report
- --------------------------------------------------------------------------------------------------------------------
Statements of Assets and Liabilities                   December 31, 1998


                                                                                  Wanger U.S.   Wanger International
                                                                                    Small Cap              Small Cap
- ---------------------------------------------------------------------------------------------------------------------
<S>                                                                             <C>                      <C>
Assets
Investments, at value (cost: Wanger U.S. Small Cap $291,173,961;                 $341,278,819            $141,152,080

     Wanger International Small Cap $114,598,402)

Cash                                                                                      900                      --
Organization costs                                                                     26,688                  26,688
Receivable for:
     Securities sold                                                                  128,796                 320,926
     Fund shares sold                                                                 455,068                  18,010
     Dividends and interest                                                            78,895                 158,549
     Other assets                                                                       3,366                   2,275
- ---------------------------------------------------------------------------------------------------------------------
     Total assets                                                                 341,972,532             141,678,528



Liabilities and Net Assets
Cash Overdraft                                                                             --                  19,998
Payable for:
     Securities purchased                                                           2,644,341                 255,760
     Fund shares redeemed                                                             142,326                  53,377
     Amount owed to advisor                                                            27,098                  26,732
     Other                                                                             39,886                  69,352
- ---------------------------------------------------------------------------------------------------------------------
     Total liabilities                                                              2,853,651                 425,219
- ---------------------------------------------------------------------------------------------------------------------
Net assets applicable to Fund shares outstanding                                 $339,118,881            $141,253,309
- ---------------------------------------------------------------------------------------------------------------------
Fund shares outstanding                                                            15,290,823               7,197,954
- ---------------------------------------------------------------------------------------------------------------------
Pricing of Shares
Net asset value, offering price and redemption price per share                         $22.18                  $19.62
- ---------------------------------------------------------------------------------------------------------------------
Analysis of Net Assets
Paid-in capital                                                                  $258,403,736            $119,664,782
Undistributed net realized gain (loss) on sales of investments                     30,610,287              (7,277,677)
Net unrealized appreciation of investments and foreign currency
transactions


    (net of unrealized PFIC gains of $83,762 for Wanger International Small Cap)   50,104,858              26,470,102

Undistributed net investment income                                                        --               2,396,102
- ---------------------------------------------------------------------------------------------------------------------
Net assets applicable to Fund shares outstanding                                 $339,118,881            $141,253,309
- ---------------------------------------------------------------------------------------------------------------------

</TABLE>

See accompanying notes to financial statements.

                                       56
<PAGE>
 
                                       Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Statements of Operations               For the Year Ended December 31, 1998
<TABLE> 
<CAPTION> 

                                                                                   Wanger U.S.           Wanger International
                                                                                     Small Cap                      Small Cap
- -----------------------------------------------------------------------------------------------------------------------------
<S>                                                                                <C>                            <C>
 
Investment Income:
Dividends (net of foreign taxes of $220,936 for Wanger International Small Cap)    $ 1,186,818                   $  1,946,183 
Interest                                                                             1,201,904                        408,617 
- -----------------------------------------------------------------------------------------------------------------------------
     Total investment income                                                         2,388,722                      2,354,800
                                                                                                                              
- -----------------------------------------------------------------------------------------------------------------------------
Expenses:                                                                                                                     
Investment advisory                                                                   2,972,442                     1,751,136
Custodian                                                                                42,548                       233,512
Legal and audit                                                                          44,236                        42,701
Reports to shareholders                                                                  35,986                        36,902
Amortization of organization costs                                                       19,976                        19,976
Transfer agent                                                                           22,675                        19,500
Trustees                                                                                 20,787                        20,787
Insurance                                                                                 3,067                         2,450
Other                                                                                    16,257                         8,483
- -----------------------------------------------------------------------------------------------------------------------------
     Total expenses                                                                   3,177,974                     2,135,447
     Less custodian fees paid indirectly                                                 (5,829)                         (785)
- -----------------------------------------------------------------------------------------------------------------------------
     Net expenses                                                                     3,172,145                     2,134,662
- -----------------------------------------------------------------------------------------------------------------------------  
Net investment income (loss)                                                           (783,423)                      220,138
Net realized and unrealized gain (loss) on investments:                                                      
     Net realized gain (loss) on sales of investments                                31,406,965                    (2,995,916)
     Net change in unrealized appreciation of investments                            (6,414,368)                   21,548,547
- -----------------------------------------------------------------------------------------------------------------------------
Net realized and unrealized gain on investments                                      24,992,597                    18,552,631
- -----------------------------------------------------------------------------------------------------------------------------
Net increase in net assets resulting from operations                               $ 24,209,174                  $ 18,772,769
- -----------------------------------------------------------------------------------------------------------------------------

</TABLE>

See accompanying notes to financial statements.

                                       57
<PAGE>
 
                   Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Statements of Changes in Net Assets


<TABLE>
<CAPTION>
                                                --------------------------------------    --------------------------------------
                                                Wanger U.S. Small Cap                     Wanger International Small Cap

                                                       Year ended           Year ended           Year ended           Year ended
                                                December 31, 1998    December 31, 1997    December 31, 1998    December 31, 1997
- --------------------------------------------------------------------------------------------------------------------------------
<S>                                             <C>                  <C>                  <C>                  <C>
From operations:
Net investment income (loss)                         $   (783,423)        $   (206,969)        $    220,138         $    148,271
Net realized gain (loss) on sales of investments       31,406,965           15,616,554           (2,995,916)            (616,933)
Net change in unrealized appreciation                  (6,414,368)          37,057,494           21,548,547           (2,999,052)
- --------------------------------------------------------------------------------------------------------------------------------
     Net increase (decrease) in net assets
     resulting from operations                         24,209,174           52,467,079           18,772,769           (3,467,714)
Distributions to shareholders from:
Net investment income                                          --                   --           (1,532,876)                  --
Net realized gain                                     (15,422,770)          (3,530,225)                  --           (2,453,253)
- --------------------------------------------------------------------------------------------------------------------------------
     Total distributions to shareholders              (15,422,770)          (3,530,225)          (1,532,876)          (2,453,253)

From Fund share transactions:
Reinvestment of dividends and capital
     gain distributions                                15,407,847            3,530,225            1,530,069            2,453,253
Proceeds from other shares sold                        94,608,919          109,491,784           26,836,486           54,111,870
- --------------------------------------------------------------------------------------------------------------------------------
                                                      110,016,766          113,022,009           28,366,555           56,565,123
Payments for shares redeemed                          (50,550,116)         (20,050,947)         (25,013,297)         (14,839,080)
- --------------------------------------------------------------------------------------------------------------------------------
     Net increase in net assets from
     Fund share transactions                           59,466,650           92,971,062            3,353,258           41,726,043
- --------------------------------------------------------------------------------------------------------------------------------
Total increase in net assets                           68,253,054          141,907,916           20,593,151           35,805,076
- --------------------------------------------------------------------------------------------------------------------------------
Net assets:
Beginning of period                                   270,865,827          128,957,911          120,660,158           84,855,082
- --------------------------------------------------------------------------------------------------------------------------------
End of period (a)                                    $339,118,881         $270,865,827         $141,253,309         $120,660,158
- --------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(a) Includes accumulated net investment income
of $2,396,211 and $1,532,855 for Wanger International Small Cap
at December 31, 1998 and 1997, respectively.



See accompanying notes to financial statements.

                                      58
<PAGE>
 
                   Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Wanger U.S. Small Cap                  Financial Highlights


<TABLE>
<CAPTION>
                                                        Year ended           Year ended           Year ended   May 3, 1995 through
                                                 December 31, 1998    December 31, 1997    December 31, 1996      December 31,1995

- ----------------------------------------------------------------------------------------------------------------------------------
<S>                                              <C>                  <C>                  <C>                 <C>
Net Asset Value, beginning of period                  $      21.46         $      16.97         $      11.60           $     10.00

Income From Investment Operations
   Net investment loss (c)                                    (.05)                (.02)                (.06)                 (.05)
   Net realized and unrealized gain on investments            1.93                 4.90                 5.46                  1.65
- ----------------------------------------------------------------------------------------------------------------------------------
   Total from investment operations                           1.88                 4.88                 5.40                  1.60

Less Distributions
   Dividends from net investment income                         --                   --                   --                    --
   Distributions from net realized gain                      (1.16)                (.39)                (.03)                   --
- ----------------------------------------------------------------------------------------------------------------------------------
   Total distributions                                       (1.16)                (.39)                (.03)                   --

Net Asset Value, end of period                        $      22.18         $      21.46         $      16.97           $     11.60
- ----------------------------------------------------------------------------------------------------------------------------------

Total Return                                                  8.68%               29.41%               46.59%                16.00%

Ratios/Supplemental Data
Ratio of expenses to average net assets (a) (b)               1.02%                1.06%                1.21%                 2.08%
Ratio of net investment loss to average net assets (b)        (.25%)               (.10%)               (.41%)               (1.44%)
Portfolio turnover rate                                         34%                  34%                  46%                   59%
Net assets at end of period                           $339,118,881         $270,865,827         $128,957,911           $21,903,536


- ----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

     *Annualized

(a)  In accordance with a requirement of the Securities and Exchange Commission,
     this 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 1.04% for the year ended December 31, 1997, 1.19% for the year ended
     December 31, 1996 and 2.00% for the period ended December 31, 1995.

(b)  The fund was reimbursed by the Advisor for certain expenses from May 3,
     1995 through December 31, 1995. 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 for the period
     ended December 31, 1995 would have been 2.35% and (1.71%), respectively.

(c)  Net investment loss per share for the years ended December 31, 1998, 1997
     and 1996 was based upon the average shares outstanding during the period.


See accompanying notes to financial statements.

                                      59
<PAGE>
 
                                 Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Wanger International Small Cap   Financial Highlights

<TABLE>
<CAPTION>

                                                           Year ended          Year ended          Year ended   May 3, 1995 through
                                                    December 31, 1998   December 31, 1997   December 31, 1996     December 31, 1995
<S>                                                 <C>                 <C>                 <C>                 <C>
====================================================================================================================================
Net Asset Value, beginning of period                           $17.05              $17.71              $13.45              $10.00

Income From Investment Operations
   Net investment income (loss)(c)                                .03                 .02                (.09)               (.03)
   Net realized and unrealized gain on investments               2.76                (.26)              (4.38)              (3.48)
- ------------------------------------------------------------------------------------------------------------------------------------
   Total from investment operations                              2.79                (.24)               4.29                3.45

Less Distributions
Dividends from net investment income                             (.22)                 --                  --                  --
 Distributions from net realized gain and unrealized
 gain reportable for federal income taxes                          --                (.42)               (.03)                 --
- ------------------------------------------------------------------------------------------------------------------------------------
   Total distributions                                           (.22)               (.42)               (.03)                 --

Net Asset Value, end of period                                 $19.62              $17.05              $17.71              $13.45
- ------------------------------------------------------------------------------------------------------------------------------------

Total Return                                                    16.33%              (1.46%)             32.01%              34.50%

Ratios/Supplemental Data Ratio of expenses to
 average net assets (a)(b)                                       1.55%               1.60%               1.79%               2.32%*
Ratio of net investment income (loss)
 to average net assets (b)                                        .16%                .12%               (.56%)              (.81%)*
Portfolio turnover rate                                            56%                 60%                 50%                 14%*
Net assets at end of period                               141,253,309         120,660,158          84,855,082          11,368,924
- ------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

    *Annualized

(a) In accordance with a requirement of the Securities and Exchange Commission,
    this 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 1.59% for the year ended December 31, 1997, 1.75% for the year ended
    December 31, 1996 and 2.00% for the period ended December 31, 1995.

(b) The fund was reimbursed by the Advisor for certain expenses from May 3, 1995
    through December 31, 1995. 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 for the period ended
    December 31, 1995 would have been 4.20% and (2.69%), respectively.

(c) Net investment income (loss) per share for the years ended December 31,
    1998, 1997 and 1996 was based upon the average shares outstanding during the
    period.

See accompanying notes to financial statements.

                                      60
<PAGE>
 
                              Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Notes to Financial Statements


1. Nature of Operations 

Wanger U.S. Small Cap and Wanger International Small Cap ("the Funds") are
series of Wanger Advisors Trust ("the Trust"), an open-end management investment
company organized as a Massachusetts business trust. The investment objective of
each Fund is to seek long-term growth of capital. The Funds are available only
for allocation to certain life insurance company separate accounts established
for the purpose of funding qualified and non-qualified variable annuity
contracts, and may also be offered directly to certain types of pension plans
and retirement arrangements.

2. Significant Accounting Policies

Security valuation

Investments are stated at current value. Securities traded on securities
exchanges or in over-the-counter markets in which transaction prices are
reported are valued at the last sales price at the time of valuation. Securities
for which there are no reported sales on the valuation date are valued at the
mean of the latest bid and ask quotation or, if there is no ask quotation, at
the most recent bid quotation. Money market instruments having a maturity of 60
days or less from the valuation date are valued on an amortized cost basis.
Securities for which quotations are not readily available and any other assets
are valued as determined in good faith by the Board of Trustees.

Foreign currency translations

Values of investments denominated in foreign currencies are converted into U.S.
dollars using the spot market rate of exchange at the time of valuation.
Purchases and sales of investments and dividend and interest income are
translated into U.S. dollars using the spot market rate of exchange prevailing
on the respective dates of such transactions. The gain or loss resulting from
changes in foreign exchange rates is included with net realized and unrealized
gain or loss from investments, as appropriate.

Security transactions and investment income

Security transactions are accounted for on the trade date (date the order to buy
or sell is executed) and dividend income is recorded on the ex-dividend date,
except that certain dividends from foreign securities are recorded as soon as
the information is available to the Fund. Interest income is recorded on the
accrual basis and includes amortization of discounts on money market instruments
and on long-term debt instruments when required for federal income tax purposes.
Realized gains and losses from security transactions are reported on an
identified cost basis.

Use of estimates

The preparation of financial statements in conformity with generally accepted
counting principles requires management to make estimates and assumptions that
affect the amounts reported in the financial statements and accompanying notes.
Actual results may differ from those estimated.

Fund share valuation

Fund shares are sold and redeemed on a continuing basis at net asset value. Net
asset value per share is determined daily as of the close of trading on the New
York Stock Exchange on each day the Exchange is open for trading by dividing the
total value of the Fund's investments and other assets, less liabilities, by the
number of Fund shares outstanding.

Custodian fees

Custodian fees are reduced based on each Fund's cash balances maintained with
the custodian. This presentation does not affect the determination of Fund
shares outstanding.

Federal income taxes, dividends and distributions to shareholders

The Funds have complied with the special provisions of the Internal Revenue Code
available to regulated investment companies and, in the manner provided therein,
distribute all of their taxable income, as well as any net realized gain on
sales of investments and foreign currency transactions reportable for federal
income tax purposes.

  Wanger International Small Cap has elected to mark-to-market its investments
in Passive Foreign Investment Companies ("PFICS") for income tax purposes. In
accordance with this election, the Fund recognized unrealized appreciation on
PFICs of $83,762 for the year ended December 31, 1998. Cumulative net unrealized
appreciation recognized in prior years on PFICs sold in 1998 amounted to
$1,391,583.

  Wanger International Small Cap intends to utilize provisions of the federal
income tax law that allows it to carry a realized capital loss forward for eight
years following the year of the loss and offset such losses against future
realized gains. At December 31, 1998, the Fund had a capital loss carryforward
of $7,263,202 of which $382,694 will expire December 31, 2005 and $6,880,508
will expire December 31, 2006.

  Dividends and distributions payable to each Fund's shareholders are recorded
by the Fund on the ex-dividend date.

  Reclassifications have been made in 1998 for Wanger U.S. Small Cap in the
accompanying analysis of net assets from undistributed net investment income
to net realized gain on the sale of investments of $783,423 to reflect
differences between financial reporting and income tax basis and had no impact
on net asset value. Reclassifications have also been made in 1998 for Wanger
International Small Cap from accumulated net realized gain on sale of
investments to undistributed net investment income of $2,092,223 to reflect
differences between financial reporting and income tax basis.

                                      61
<PAGE>
 
                                       Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Notes to Financial Statements



3.  Transaction with Affiliates

The Fund's investment advisor, Wanger Asset Management, L.P., ("WAM") furnishes
continuing investment supervision to the Fund and is responsible for overall
management of the Fund's business affairs.  Each Fund pays WAM a monthly
advisory fee based upon average daily net assets at the following rates:

<TABLE>
<CAPTION>
                               Wanger U.S.   Wanger International
                                Small Cap          Small Cap
- ------------------------------------------------------------------
<S>                            <C>           <C>
Average Daily Net Assets:
 For the first $100 million       1.00%             1.30%
 Next $150 million                 .95%             1.20%
 In excess of $250 million         .90%             1.10%
- ------------------------------------------------------------------
</TABLE>

  The investment advisory agreement also provides that WAM will reimburse the
Funds to the extent that ordinary operating expenses (computed based on net
custodian fees) exceed 1.50% for Wanger U.S. Small Cap and 1.90% for Wanger
International Small Cap, of average net assets. WAM was not required to
reimburse the Funds under these agreements for the year ended December 31, 1998.

  Certain officers and trustees of the Trust are also principals of WAM. The
Trust makes no direct payments to its officers and trustees who are affiliated
with WAM. Wanger U.S. Small Cap and Wanger International Small Cap each incurred
trustees' fees and expenses of $20,787 for the year ended December 31, 1998 to
trustees not affiliated with WAM.

  WAM advanced $100,000 in connection with the organization and initial
registration of the Fund. These costs are being amortized and reimbursed to WAM
over the period May, 1995 through April, 2000.

  WAM Brokerage Services, L.L.C., a wholly-owned subsidiary of WAM, is the
distributor of each Fund's shares and receives no compensation for its services.

4.  Borrowing Arrangements
The trust participates in a $250,000,000 credit facility which was entered into
to facilitate portfolio liquidity. No amounts have been borrowed under this
facility.

5.  Fund Share Transactions

Proceeds and payments on Fund shares as shown in the statement of changes in net
assets are in respect of the following numbers of shares:

<TABLE>
<CAPTION>
                                          ------------------------------------------   --------------------------------------
                                          Wanger U.S.Small Cap                         Wanger International Small Cap

                                                      Year ended          Year ended          Year ended           Year ended
                                               December 31, 1998   December 31, 1997   December 31, 1998    December 31, 1997
- -----------------------------------------------------------------------------------------------------------------------------
<S>                                           <C>                 <C>                 <C>                  <C>
Shares sold                                            4,370,518           5,806,192           1,389,310            2,963,636
Shares issued in reinvestment of dividend and
capital gain distributions                               686,318             210,886              76,657              136,747
- -----------------------------------------------------------------------------------------------------------------------------
                                                       5,056,836           6,017,078           1,465,967            3,100,383
Less shares redeemed                                   2,389,858             991,354           1,346,776              812,741
- -----------------------------------------------------------------------------------------------------------------------------
Net increase in shares outstanding                     2,666,978           5,025,724             119,191            2,287,642
=============================================================================================================================

</TABLE>

6.    Investment Transactions

The aggregate costs of purchases and proceeds from sales other than short-term
obligations for the year ended December 31, 1998 were:
<TABLE> 
<CAPTION> 

<S>                        <C>            <C>  
                            Wanger U.S.   Wanger International
                              Small Cap              Small Cap

Purchases                  $139,040,448            $80,409,567
Sales                        97,581,546             71,890,345
- ------------------------------------------------------------------------
</TABLE> 

                                       62
<PAGE>
 
Wanger Advisors Trust  1998 Annual Report
- --------------------------------------------------------------------------------
Report of Independent Auditors


To the Board of Trustees and Shareholders of
Wanger Advisors Trust

We have audited the accompanying statements of assets and liabilities, including
the schedule of investments of Wanger U.S. Small Cap and the Wanger
International Small Cap portfolios, comprising the Wanger Advisors Trust, as of
December 31, 1998, the related statements of operations, changes in net assets,
and the financial highlights for the periods indicated therein. These financial
statements and financial highlights are the responsibility of the Funds'
management. Our responsibility is to express an opinion on these financial
statements and financial highlights based on our audits.

We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements and financial
highlights are free of material misstatement. An audit includes examining, on a
test basis, evidence supporting the amounts and disclosures in the financial
statements. Our procedures included confirmation of investments owned as of
December 31, 1998, by correspondence with the custodian and brokers. An audit
also includes assessing the accounting principles used and significant estimates
made by management, as well as evaluating the overall financial statement 
presentation. We believe that our audits provide a reasonable basis for our
opinion.

In our opinion, the financial statements and financial highlights referred to
above present fairly, in all material respects, the financial position of each
of the respective Funds of the Wanger Advisors Trust as of December 31, 1998,
the results of their operations and changes in their net assets and financial
highlights for the periods indicated therein, in conformity with generally
accepted accounting principles.


                                                               ERNST & YOUNG LLP

Chicago, Illinois
February 12, 1999

                                      63


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