MORGAN STANLEY DEAN WITTER NORTH AMERICAN GOVERNMENT INCOME, 497, 2001-01-05

MORGAN STANLEY DEAN WITTER NORTH AMERICAN GOVERNMENT INCOME
497, 2001-01-05

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Filed Pursuant to Rule 497(c)
Registration File No.: 811-6572

PROSPECTUS - DECEMBER 29, 2000

MORGAN STANLEY DEAN WITTER

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

NORTH AMERICAN GOVERNMENT INCOME TRUST

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A MUTUAL FUND THAT SEEKS TO EARN A HIGH
LEVEL OF CURRENT INCOME WHILE MAINTAINING
RELATIVELY LOW VOLATILITY OF PRINCIPAL

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.

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CONTENTS

The Fund Investment Objective ..............................1

Principal Investment Strategies ...................1

Principal Risks ...................................3

Past Performance ..................................7

Fees and Expenses .................................8

Additional Investment Strategy Information ........8

Additional Risk Information .......................9

Fund Management ..................................10

Shareholder Information Pricing Fund Shares ..............................11

How to Buy Shares ................................11

How to Exchange Shares ...........................13

How to Sell Shares ...............................15

Distributions ....................................16

Tax Consequences .................................17

Financial Highlights .................................................18

Our Family of Funds ................................. Inside Back Cover

This Prospectus contains important information about the Fund.
Please read it carefully and keep it for future reference.

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THE FUND

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INVESTMENT OBJECTIVE
--------------------

Morgan Stanley Dean Witter North American Government Income Trust (the "Fund")
seeks to earn a high level of current income while maintaining relatively low
volatility of principal.

(sidebar)
INCOME
An investment objective having the goal of selecting securities to pay out
income rather than rise in price.
(end sidebar)

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

The Fund will normally invest at least 65% of its assets in fixed-income
securities issued or guaranteed by the United States, Canadian or Mexican
governments, their subdivisions, agencies or instrumentalities. These securities
are referred to generally as "government securities." In the case of the United
States and Canada, a substantial portion of these securities will be
mortgage-backed securities.

The Fund will normally invest at least 50% of its net assets in U.S. government
securities, and no more than 25% each in Canadian or Mexican government
securities. The Fund will invest in fixed-income securities that are investment
grade; the Fund's investments in Canadian government securities, however, will
be rated at least A by Moody's Investors Services Inc. ("Moody's") or Standard &
Poor's Corporation ("S&P") or, if not rated, determined to be of comparable
quality by the Fund's "Sub-Advisor," TCW Investment Management Company.

The Sub-Advisor will allocate Fund assets among the three countries based on its
analysis of market, economic and political conditions in those countries. When
deciding whether to buy, hold or sell a security for the Fund, the Sub-Advisor
will consider various factors, such as changes in interest rates and currency
exchange rates, to attempt to take advantage of favorable investment
opportunities in each country. The Sub-Advisor expects that, under normal
circumstances, the weighted average maturity (or period until the next time the
interest rate is reset) of the Fund's investment securities will be no greater
than 3 years. In addition, the Fund will purchase Mexican government securities
that have remaining maturities of one year or less.

MORTGAGE-BACKED SECURITIES. One type of mortgage-backed security, in which the
Fund may invest, is a mortgage pass-through security. These securities represent
a participation interest in a pool of residential mortgage loans originated by
governmental or private lenders such as banks. They differ from conventional
debt securities, which provide for periodic payment of interest in fixed amounts
and principal payments at maturity or on specified call dates. Mortgage
pass-through securities provide for monthly payments that are a "pass-through"
of the monthly interest and principal payments made by the individual borrowers
on the pooled mortgage loans.

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The U.S. mortgage pass-through securities in which the Fund may invest include
those issued or guaranteed by the Government National Mortgage Association
("GNMA" or "Ginnie Mae"), the Federal National Mortgage Association ("FNMA" or
"Fannie Mae") and the Federal Home Loan Mortgage Corporation ("FHLMC" or
"Freddie Mac"). GNMA certificates are backed by the "full faith and credit" of
the United States. FNMA and FHLMC certificates are not backed by the full faith
and credit of the United States but the issuing agency or instrumentality has
the right to borrow, to meet its obligations, from an existing line of credit
with the U.S. Treasury.

COLLATERALIZED MORTGAGE OBLIGATIONS. The Fund may invest in "CMOs" --
collateralized mortgage obligations. CMOs are debt obligations collateralized by
mortgage loans or mortgage pass-through securities (collectively "Mortgage
Assets"). Payments of principal and interest on the Mortgage Assets and any
reinvestment income are used to make payments on the CMOs. CMOs are issued in
multiple classes. Each class has a specific fixed or floating coupon rate and a
stated maturity or final distribution date. The principal and interest on the
Mortgage Assets may be allocated among the classes in a number of different
ways. Certain classes will, as a result of the collection, have more predictable
cash flows than others. As a general matter, the more predictable the cash flow,
the lower the yield relative to other Mortgage Assets. The less predictable the
cash flow, the higher the yield and the greater the risk. The Fund may invest in
any class of CMO.

INVERSE FLOATERS. The Fund may invest up to 10% of its net assets in inverse
floaters. An inverse floater has a coupon rate that moves in the direction
opposite to that of a designated interest rate index.

STRIPPED MORTGAGE-BACKED SECURITIES. The Fund may purchase stripped
mortgage-backed securities, which are usually structured in two classes. One
class entitles the holder to receive all or most of the interest but little or
none of the principal of a pool of Mortgage Assets (the interest-only or "IO"
Class), while the other class entitles the holder to receive all or most of the
principal but little or none of the interest (the principal-only or "PO" Class).

OTHER SECURITIES. The Fund may invest up to 35% of its net assets in securities
that are not government securities. This group of securities also will be issued
by U.S., Canadian or Mexican issuers and may include corporate debt securities
and securities backed by other assets, such as automobile or credit card
receivables or home equity loans. They are rated at least Aa by Moody's or AA by
S&P or, if not rated, determined to be of comparable quality by the Sub-Advisor.

Fixed-income securities are debt securities and can take the form of bonds,
notes or commercial paper. The issuer of the debt security borrows money from
the investor who buys the security. Most debt securities pay either fixed or
adjustable rates of interest at regular intervals until they mature, at which
point investors get their

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principal back. The Fund's fixed-income investments may include zero coupon
securities, which are purchased at a discount and either (i) pay no interest, or
(ii) accrue interest, but make no payments until maturity.

In addition, the Fund may invest in futures, options, reverse repurchase
agreements and dollar rolls.

In pursuing the Fund's investment objective, the Sub-Advisor has considerable
leeway in deciding which investments it buys, holds or sells on a day-to-day
basis -- and which trading or investment strategies it uses. For example, the
Sub-Advisor in its discretion may determine to use some permitted trading or
investment strategies while not using others.

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PRINCIPAL RISKS
---------------

There is no assurance that the Fund will achieve its investment objective. The
Fund's share price will fluctuate with changes in the market value of the Fund's
portfolio securities. When you sell Fund shares, they may be worth less than
what you paid for them and, accordingly, you can lose money investing in this
Fund.

FIXED-INCOME SECURITIES. All fixed-income securities are subject to two types of
risk: credit risk and interest rate risk. Credit risk refers to the possibility
that the issuer of a security will be unable to make interest payments and/or
repay the principal on its debt. While the Fund invests in investment grade
securities, these securities may have speculative characteristics.

Interest rate risk refers to fluctuations in the value of a fixed-income
security resulting from changes in the general level of interest rates. When the
general level of interest rates goes up, the prices of most fixed-income
securities go down. When the general level of interest rates goes down, the
prices of most fixed-income securities go up. (Zero coupon securities are
typically subject to greater price fluctuations than comparable securities that
pay interest.)

MORTGAGE-BACKED SECURITIES. Mortgage-backed securities have different risk
characteristics than traditional debt securities. Although generally the value
of fixed-income securities increases during periods of falling interest rates
and decreases during periods of rising interest rates, this is not always the
case with mortgage-backed securities. This is due to the fact that principal on
underlying mortgages may be prepaid at any time as well as other factors.
Generally, prepayments will increase during a period of falling interest rates
and decrease during a period of rising interest rates. The rate of prepayments
also may be influenced by economic and other factors. Prepayment risk includes
the possibility that, as interest rates fall, securities with stated interest
rates may have the principal prepaid earlier than expected, requiring the Fund
to invest the proceeds at generally lower interest rates.

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Investments in mortgage-backed securities are made based upon, among other
things, expectations regarding the rate of prepayments on underlying mortgage
pools. Rates of prepayment, faster or slower than expected by the Sub-Advisor,
could reduce the Fund's yield, increase the volatility of the Fund and/or cause
a decline in net asset value. Certain mortgage-backed securities in which the
Fund may invest may be more volatile and less liquid than other traditional
types of debt securities. The Fund may be subject to a risk referred to as
"extension risk," which is the possibility that rising interest rates may cause
owners of the underlying mortgages to pay off their mortgages at a slower than
expected rate. This risk may effectively change a security that was short or
intermediate term into a long term security. Long term securities generally drop
in value more dramatically when the general level of interest rates goes up.

CMOs. Certain mortgage-backed securities in which the Fund may invest (e.g.,
certain classes of CMOs) may increase or decrease in value substantially with
changes in interest rates and/or the rates of prepayment. In addition, if the
collateral securing CMOs or any third party guarantees are insufficient to make
payments, the Fund could sustain a loss.

INVERSE FLOATERS. Like most other fixed-income securities, the value of inverse
floaters will decrease as interest rates increase. They are more volatile,
however, than most other fixed-income securities because the coupon rate on an
inverse floater typically changes at a multiple of the change in the relevant
index rate. Thus, any rise in the index rate (as a consequence of an increase in
interest rates) causes a correspondingly greater drop in the coupon rate of an
inverse floater while a drop in the index rate causes a correspondingly greater
increase in the coupon of an inverse floater. The value of some inverse floaters
may also increase or decrease substantially because of changes in the rate of
prepayments.

STRIPPED MORTGAGE-BACKED SECURITIES. IOs tend to decrease in value substantially
if interest rates decline and prepayment rates become more rapid. POs tend to
decrease in value substantially if interest rates increase and the rate of
repayment decreases.

FOREIGN SECURITIES. Foreign securities involve risks in addition to the risks
associated with domestic securities. One additional risk is currency risk. While
the price of Fund shares is quoted in U.S. dollars, the Fund generally converts
U.S. dollars to a foreign market's local currency to purchase a security in that
market. If the value of that local currency falls relative to the U.S. dollar,
the U.S. dollar value of the foreign security will decrease. This is true even
if the foreign security's local price remains unchanged.

Foreign securities also have risks related to economic and political
developments abroad, including effects of foreign social, economic or political
instability. Foreign issuers, in general, are not subject to the regulatory
requirements of U.S. issuers and, as such, there may be less publicly available
information about these issuers. Moreover, foreign accounting, auditing and
financial reporting standards generally are different

<PAGE>

from those applicable to U.S. issuers. Finally, in the event of a default of any
foreign debt obligations, it may be more difficult for the Fund to obtain or
enforce a judgment against the issuers of the securities.

Securities of foreign issuers may be less liquid than comparable securities of
U.S. issuers and, as such, their price changes may be more volatile.
Furthermore, foreign exchanges and broker-dealers are generally subject to less
government and exchange scrutiny and regulation than their U.S. counterparts. In
addition, differences in clearance and settlement procedures in foreign markets
may occasion delays in settlement of the Fund's trades effected in those markets
and could result in losses to the Fund due to subsequent declines in the value
of the securities subject to the trades.

The Mexican securities in which the Fund may invest are issued by a developing
country. Compared to the United States and other developed countries, developing
countries may have relatively unstable governments, economies based on only a
few industries and securities markets that trade a small number of securities.
Prices of these securities tend to be especially volatile and, in the past,
securities in these countries have offered greater potential loss than
securities of companies located in developed countries.

CANADIAN AND MEXICAN SECURITIES. The Canadian debt securities market is
significantly smaller than the U.S. debt securities market. In particular, the
Canadian mortgage-backed securities market is of recent origin, and, although
continued growth is anticipated, is less well developed and less liquid than its
U.S. counterpart.

Because the Fund may invest in Mexican debt instruments, investors in the Fund
should be aware of certain special considerations associated with investing in
debt obligations of the Mexican government.

The Mexican government has exercised and continues to exercise a significant
influence over many aspects of the private sector in Mexico. Mexican government
actions concerning the economy could have a significant effect on market
conditions and prices and yields of Mexican debt obligations, including those in
which the Fund invests. Mexico is currently a major debtor nation (among
developing countries) to commercial banks and foreign governments.

The value of the Fund's investments may be affected by changes in oil prices,
interest rates, taxation and other political or economic developments in Mexico,
including recent rates of inflation which have exceeded the rates of inflation
in the U.S. and Canada. The Fund can provide no assurance that future
developments in the Mexican economy will not impair the Fund's investment
flexibility, operations or ability to achieve its investment objective.

<PAGE>

OTHER RISKS. The performance of the Fund also will depend on whether the
Sub-Advisor is successful in pursuing the Fund's investment strategy. In
addition, the Fund is subject to other risks from its permissible investments
including those risks associated with futures, options and reverse repurchase
agreements and dollar rolls. For information about these risks, see the
"Additional Risk Information" section.

Shares of the Fund are not bank deposits and are not guaranteed or insured by
the FDIC or any other government agency.

<PAGE>

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PAST PERFORMANCE
----------------

The bar chart and table below provide some indication of the risks of investing
in the Fund. The Fund's past performance does not indicate how the Fund will
perform in the future.

(sidebar)
ANNUAL TOTAL RETURNS
This chart shows how the performance of the Fund's shares has varied from year
to year over the past 7 calendar years.
(end sidebar)

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ANNUAL TOTAL RETURNS -- CALENDAR YEARS

Percentage 8.11% -15.59% 16.00% 4.01% 7.89% 6.75% 2.35%
--------------------------------------------------------------------------------
Year 1993 1994 1995 1996 1997 1998 1999

Year-to-date total return as of September 30, 2000 was 5.43%.

During the periods shown in the bar chart, the highest return for a calendar
quarter was 5.65% (quarter ended June 30, 1995) and the lowest return for a
calendar quarter was -10.51% (quarter ended December 31, 1994).

(sidebar)
AVERAGE ANNUAL TOTAL RETURNS
This table compares the Fund's average annual total returns with those of a
broad measure of market performance over time.
(end sidebar)

AVERAGE ANNUAL TOTAL RETURNS (AS OF DECEMBER 31, 1999)
--------------------------------------------------------------------------------
LIFE OF FUND
PAST 1 YEAR PAST 5 YEARS (SINCE 7/31/92)
--------------------------------------------------------------------------------
Morgan Stanley Dean Witter
North American Government
Income Trust 2.35% 7.30% 4.05%
--------------------------------------------------------------------------------
Lehman Brothers U.S.
Government Index (1-5 Year)(1) 1.96% 6.74% 5.60%
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1 The Lehman Brothers U.S. Government Index (1-5 Year) measures the performance
of all U.S. government agency and Treasury securities with maturities of one
to five years. The Index does not include any expenses, fees or charges. The
Index is unmanaged and should not be considered an investment.

<PAGE>

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FEES AND EXPENSES
-----------------

The table below briefly describes the fees and expenses that you may pay if you
buy and hold shares of the Fund. The Fund does not impose any initial or
deferred sales charges and does not charge account or exchange fees.

(sidebar)
ANNUAL FUND OPERATING EXPENSES
These expenses are deducted from the Fund's assets and are based on expenses
paid for the fiscal year ended October 31, 2000.
(end sidebar)

Annual Fund Operating Expenses
--------------------------------------------------------------------------------
Management fee 0.65%
--------------------------------------------------------------------------------
Distribution and service (12b-1) fees 0.74%
--------------------------------------------------------------------------------
Other expenses 0.37%
--------------------------------------------------------------------------------
Total annual Fund operating expenses 1.76%
--------------------------------------------------------------------------------

EXAMPLE

This example is intended to help you compare the cost of investing in the Fund
with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the Fund, your investment has a
5% return each year, and the Fund's operating expenses remain the same. Although
your actual costs may be higher or lower, the table below shows your costs at
the end of each period based on these assumptions.

1 YEAR 3 YEARS 5 YEARS 10 YEARS
-----------------------------------------------------------
$179 $554 $954 $2,073
------------------------------------------------------------

Long-term shareholders may pay more in distribution fees than the economic
equivalent of the maximum front-end sales charges permitted by the NASD .

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ADDITIONAL INVESTMENT STRATEGY INFORMATION
------------------------------------------

This section provides additional information relating to the Fund's principal
investment strategies.

OPTIONS AND FUTURES. The Fund may invest in put and call options and futures
with respect to financial instruments and interest rate indexes. The Fund may
use options and futures to facilitate allocation of the Fund's investments among
asset classes, to increase or decrease the Fund's exposure to a bond market, to
generate income or to seek to protect against a decline in securities or an
increase in prices of securities that may be purchased.

REVERSE REPURCHASE AGREEMENTS AND DOLLAR ROLLS. The Fund may use reverse
repurchase agreements and dollar rolls as part of its investment strategy.
Reverse repurchase agreements involve sales by the Fund of portfolio assets
concurrently with an

<PAGE>

agreement by the Fund to repurchase the same assets at a later date at a fixed
price. The Fund may enter into dollar rolls in which the Fund sells securities
for delivery in the current month and simultaneously contracts to repurchase
substantially similar (same type and coupon) securities on a specified future
date.

DEFENSIVE INVESTING. The Fund may take temporary "defensive" positions in
attempting to respond to adverse market conditions. The Fund may invest any
amount of its assets in cash or money market instruments in a defensive posture
when the Sub-Advisor believes it is advisable to do so. Although taking a
defensive posture is designed to protect the Fund from an anticipated market
downturn, it could have the effect of reducing the benefit from any upswing in
the market. When the Fund takes a defensive position, it may not achieve its
investment objective.

The percentage limitations relating to the composition of the Fund's portfolio
apply at the time the Fund acquires an investment. Subsequent percentage changes
that result from market fluctuations will not require the Fund to sell any
portfolio security. The Fund may change its principal investment strategies
without shareholder approval; however, you would be notified of any changes.

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ADDITIONAL RISK INFORMATION
---------------------------

This section provides additional information relating to the principal risks of
investing in the Fund.

OPTIONS AND FUTURES. If the Fund invests in options and/or futures, its
participation in these markets would subject it to certain risks. The Investment
Manager's or Sub-Advisor's predictions of movements in the direction of the
stock, bond or interest rate markets may be inaccurate, and the adverse
consequences to the Fund (e.g., a reduction in the Fund's net asset value or a
reduction in the amount of income available for distribution) may leave the Fund
in a worse position than if these strategies were not used. Other risks inherent
in the use of options and futures include, for example, the possible imperfect
correlation between the price of options and futures contracts and movements in
the prices of the securities being hedged, and the possible absence of a liquid
secondary market for any particular instrument. Certain options may be
over-the-counter options, which are options negotiated with dealers; there is no
secondary market for these investments.

REVERSE REPURCHASE AGREEMENTS AND DOLLAR ROLLS. Reverse repurchase agreements
and dollar rolls involve the risk that the market value of the securities the
Fund is obligated to repurchase under the agreement may decline below the
repurchase price. In the event the buyer of securities under a reverse
repurchase agreement or dollar roll files for bankruptcy or becomes insolvent,
the Fund's use of proceeds of the agreement may be restricted pending a
determination by the other party, or its trustee or receiver,

<PAGE>

whether to enforce the Fund's obligation to repurchase the securities. Reverse
repurchase agreements and dollar rolls are speculative techniques involving
leverage, and are considered borrowings by the Fund.

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FUND MANAGEMENT
---------------

(sidebar)
MORGAN STANLEY DEAN WITTER ADVISORS INC.
The Investment Manager is widely recognized as a leader in the mutual fund
industry and together with Morgan Stanley Dean Witter Services Company Inc.,
its wholly-owned subsidiary, had approximately $150 billion in assets under
management as of November 30, 2000.
(end sidebar)

The Fund has retained the Investment Manager - Morgan Stanley Dean Witter
Advisors Inc. - to provide administrative services and manage its business
affairs. The Investment Manager has, in turn, contracted with the Sub-Advisor -
TCW Investment Management Company - to invest the Fund's assets, including the
placing of orders for the purchase and sale of portfolio securities. Prior to
June 28, 1999, TCW Investment Management Company acted as the Fund's advisor and
Morgan Stanley Dean Witter Services Company Inc., a wholly-owned subsidiary of
the Investment Manager, served as the Fund's manager. The Investment Manager is
a wholly-owned subsidiary of Morgan Stanley Dean Witter & Co., a preeminent
global financial services firm that maintains leading market positions in each
of its three primary businesses: securities, asset management and credit
services. Its main business office is located at Two World Trade Center, New
York, NY 10048.

The Sub-Advisor, together with its affiliated companies, manages approximately
$85 billion primarily for institutional investors as of September 30, 2000. The
Sub-Advisor is a wholly-owned subsidiary of TCW Group, Inc., whose direct and
indirect subsidiaries provide a variety of trust, investment management and
investment advisory services. The Sub-Advisor's main business office is located
at 865 South Figueroa Street, Suite 1800, Los Angeles, CA 90017.

Philip A. Barach and Jeffrey E. Gundlach, Group Managing Directors of the
Sub-Advisor, and Frederick H. Horton, Managing Director of the Sub-Advisor, are
the Fund's primary portfolio managers, and have been so for over five years.
Messrs. Barach, Gundlach and Horton have each been portfolio managers with
affiliates of the Sub-Advisor for over five years.

The Fund pays the Investment Manager a monthly management fee as full
compensation for the services and facilities furnished to the Fund, and for Fund
expenses assumed by the Investment Manager. The fee is based on the Fund's
average daily net assets. For the fiscal year ended October 31, 2000, the Fund
accrued total compensation to the Investment Manager amounting to 0.65% of the
Fund's average daily net assets. The Investment Manager pays the Sub-Advisor
compensation equal to 40% of its compensation for services and facilities
furnished to the Fund.

<PAGE>

SHAREHOLDER INFORMATION

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PRICING FUND SHARES
-------------------

The price of Fund shares, called "net asset value," is based on the value of the
Fund's portfolio securities.

The net asset value per share of the Fund is determined once daily at 4:00 p.m.
Eastern time on each day that the New York Stock Exchange is open (or, on days
when the New York Stock Exchange closes prior to 4:00 p.m., at such earlier
time). Shares will not be priced on days that the New York Stock Exchange is
closed.

The value of the Fund's portfolio securities is based on the securities' market
price when available. When a market price is not readily available, including
circumstances under which the Investment Manager and/or Sub-Advisor determines
that a security's market price is not accurate, a portfolio security is valued
at its fair value, as determined under procedures established by the Fund's
Board of Trustees. In these cases, the Fund's net asset value will reflect
certain portfolio securities' fair value rather than their market price. With
respect to securities that are primarily trading in foreign markets, the value
of the Fund's portfolio securities may change on days when you will not be able
to purchase or sell your shares.

An exception to the Fund's general policy of using market prices concerns its
short-term debt portfolio securities. Debt securities with remaining maturities
of sixty days or less at the time of purchase are valued at amortized cost.
However, if the cost does not reflect the securities' market value, these
securities will be valued at their fair value.

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

(sidebar)
CONTACTING A FINANCIAL ADVISOR
If you are new to the Morgan Stanley Dean Witter Family of Funds and would like
to contact a Financial Advisor, call (877) 937-MSDW (toll-free) for the
telephone number of the Morgan Stanley Dean Witter office nearest you. You may
also access our office locator on our Internet site at: www.msdwadvice.com/funds
(end sidebar)

You may open a new account to buy Fund shares or buy additional Fund shares for
an existing account by contacting your Morgan Stanley Dean Witter Financial
Advisor or other authorized financial representative. Your Financial Advisor
will assist you, step-by-step, with the procedures to invest in the Fund. You
may also purchase shares directly by calling the Fund's transfer agent and
requesting an application.

When you buy Fund shares, the shares are purchased at the next share price
calculated after we receive your purchase order. Your payment is due on the
third business day after you place your purchase order. We reserve the right to
reject any order for the purchase of Fund shares.

<PAGE>

(sidebar)
EASYINVEST(SM)
A purchase plan that allows you to transfer money automatically from your
checking or savings account or from a Money Market Fund on a semi-monthly,
monthly or quarterly basis. Contact your Morgan Stanley Dean Witter Financial
Advisor for further information about this service.
(end sidebar)

MINIMUM INVESTMENT AMOUNTS
--------------------------------------------------------------------------------
MINIMUM INVESTMENT
-----------------------
INVESTMENT OPTIONS INITIAL ADDITIONAL
--------------------------------------------------------------------------------
Regular accounts $1,000 $100
--------------------------------------------------------------------------------
Individual Retirement Accounts: Regular IRAs $1,000 $100
Education IRAs $ 500 $100
--------------------------------------------------------------------------------
EasyInvest(SM)
(Automatically from your
checking or savings account
or Money Market Fund) $ 100* $100*
--------------------------------------------------------------------------------

* Provided your schedule of investments totals $1,000 in twelve months.

There is no minimum investment amount if you purchase Fund shares through: (1)
the Investment Manager's mutual fund asset allocation plan, (2) a program,
approved by the Fund's distributor, in which you pay an asset-based fee for
advisory, administrative and/or brokerage services, (3) the following programs
approved by the Fund's distributor: (i) qualified state tuition plans described
in Section 529 of the Internal Revenue Code and (ii) certain other investment
programs that do not charge an asset-based fee, or (4) employer-sponsored
employee benefit plan accounts.

SUBSEQUENT INVESTMENTS SENT DIRECTLY TO THE FUND. In addition to buying
additional Fund shares for an existing account by contacting your Morgan Stanley
Dean Witter Financial Advisor, you may send a check directly to the Fund. To buy
additional shares in this manner:

o Write a "letter of instruction" to the Fund specifying the name(s) on the
account, the account number, the social security or tax identification number,
and the investment amount. The letter must be signed by the account owner(s).

o Make out a check for the total amount payable to: Morgan Stanley Dean Witter
North American Government Income Trust.

o Mail the letter and check to Morgan Stanley Dean Witter Trust FSB at P.O. Box
1040, Jersey City, NJ 07303.

PLAN OF DISTRIBUTION (RULE 12b-1 FEES) The Fund has adopted a Plan of
Distribution in accordance with Rule 12b-1 under the Investment Company Act of
1940. The Plan allows the Fund to pay distribution fees of up to 0.75% for the
sale and distribution of these shares. It also allows the Fund to pay for
services to shareholders. Because these fees are paid out of the Fund's assets
on an ongoing basis, over time these fees will increase the cost of your
investment and may cost you more than paying other types of sales charges.

<PAGE>

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

PERMISSIBLE FUND EXCHANGES. You may only exchange shares of the Fund for shares
of other continuously offered Morgan Stanley Dean Witter Funds if the Fund
shares were acquired in an exchange of shares initially purchased in a
Multi-Class Fund or an FSC Fund (subject to a front-end sales charge). In that
case, the shares may be subsequently re-exchanged for shares of the same Class
of any Multi-Class Fund or FSC Fund or for shares of a No-Load Fund, a Money
Market Fund or Short-Term U.S. Treasury Trust. Of course, if an exchange is not
permitted, you may sell shares of the Fund and buy another Fund's shares with
the proceeds.

See the inside back cover of this Prospectus for each Morgan Stanley Dean Witter
Fund's designation as a Multi-Class Fund, No-Load Fund, Money Market Fund or FSC
Fund. If a Morgan Stanley Dean Witter Fund is not listed, consult the inside
back cover of that fund's prospectus for its designation.

The current prospectus for each fund describes its investment objective(s),
policies and investment minimums, and should be read before investment. Since
exchanges are available only into continuously offered Morgan Stanley Dean
Witter Funds, exchanges are not available into any new Morgan Stanley Dean
Witter Fund during its initial offering period, or when shares of a particular
Morgan Stanley Dean Witter Fund are not being offered for purchase.

EXCHANGE PROCEDURES. You can process an exchange by contacting your Morgan
Stanley Dean Witter Financial Advisor or other authorized financial
representative. Otherwise, you must forward an exchange privilege authorization
form to the Fund's transfer agent -- Morgan Stanley Dean Witter Trust FSB -- and
then write the transfer agent or call (800) 869-NEWS to place an exchange order.
You can obtain an exchange privilege authorization form by contacting your
Financial Advisor or other authorized financial representative, or by calling
(800) 869-NEWS. If you hold share certificates, no exchanges may be processed
until we have received all applicable share certificates.

An exchange to any Morgan Stanley Dean Witter Fund (except a Money Market Fund)
is made on the basis of the next calculated net asset values of the funds
involved after the exchange instructions are accepted. When exchanging into a
Money Market Fund, the Fund's shares are sold at their next calculated net asset
value and the Money Market Fund's shares are purchased at their net asset value
on the following business day.

The Fund may terminate or revise the exchange privilege upon required notice.
The check writing privilege is not available for Money Market Fund shares you
acquire in an exchange.

TELEPHONE EXCHANGES. For your protection when calling Morgan Stanley Dean Witter
Trust FSB, we will employ reasonable procedures to confirm that exchange
instructions communicated over the telephone are genuine. These procedures may
include

<PAGE>

requiring various forms of personal identification such as name, mailing
address, social security or other tax identification number. Telephone
instructions also may be recorded.

Telephone instructions will be accepted if received by the Fund's transfer agent
between 9:00 a.m. and 4:00 p.m. Eastern time on any day the New York Stock
Exchange is open for business. During periods of drastic economic or market
changes, it is possible that the telephone exchange procedures may be difficult
to implement, although this has not been the case with the Fund in the past.

EXCHANGING SHARES OF ANOTHER FUND SUBJECT TO A CONTINGENT DEFERRED SALES CHARGE
("CDSC"). There are special considerations when you exchange shares subject to a
CDSC of another Morgan Stanley Dean Witter Fund for shares of the Fund. When
determining the length of time you held the shares and the corresponding CDSC
rate, any period (starting at the end of the month) during which you held shares
of the Fund will not be counted. Thus, in effect the "holding period" for
purposes of calculating the CDSC is frozen upon exchanging into the Fund.
Nevertheless, if shares subject to a CDSC are exchanged for shares of the Fund,
you will receive a credit when you sell the shares equal to the distribution
(12b-1) fees, if any, you paid on those shares while in the Fund up to the
amount of any applicable CDSC. See the prospectus of the fund that charges the
CDSC for more details.

MARGIN ACCOUNTS. If you have pledged your Fund shares in a margin account,
contact your Morgan Stanley Dean Witter Financial Advisor or other authorized
financial representative regarding restrictions on the exchange of such shares.

TAX CONSIDERATIONS OF EXCHANGES. If you exchange shares of the Fund for shares
of another Morgan Stanley Dean Witter Fund there are important tax
considerations. For tax purposes, the exchange out of the Fund is considered a
sale of Fund shares -- and the exchange into the other fund is considered a
purchase. As a result, you may realize a capital gain or loss.

You should review the "Tax Consequences" section and consult your own tax
professional about the tax consequences of an exchange.

LIMITATIONS ON EXCHANGES. Certain patterns of past exchanges and/or purchase or
sale transactions involving the Fund or other Morgan Stanley Dean Witter Funds
may result in the Fund limiting or prohibiting, at its discretion, additional
purchases and/or exchanges. Determinations in this regard may be made based on
the frequency or dollar amount of the previous exchanges or purchase or sale
transactions. You will be notified in advance of limitations on your exchange
privileges.

For further information regarding exchange privileges, you should contact your
Morgan Stanley Dean Witter Financial Advisor or call (800) 869-NEWS.

<PAGE>

[GRAPHIC OMITTED]

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

You can sell some or all of your Fund shares at any time. Your shares will be
sold at the next price calculated after we receive your order to sell as
described below.

<TABLE>
<CAPTION>
OPTIONS PROCEDURES
----------------------------------------------------------------------------------------------------------------------
<S> <C>
Contact Your To sell your shares, simply call your Morgan Stanley Dean Witter Financial Advisor or other
Financial Advisor authorized financial representative.
-------------------------------------------------------------------------------------------------
[GRAPHIC OMITTED] Payment will be sent to the address to which the account is registered or deposited in your
brokerage account.
----------------------------------------------------------------------------------------------------------------------
By Letter You can also sell your shares by writing a "letter of instruction" that includes:
[GRAPHIC OMITTED] o your account number;
o the dollar amount or the number of shares you wish to sell; and
o the signature of each owner as it appears on the account.
-------------------------------------------------------------------------------------------------
If you are requesting payment to anyone other than the registered owner(s) or that payment
be sent to any address other than the address of the registered owner(s) or pre-designated
bank account, you will need a signature guarantee. You can generally obtain a signature
guarantee from an eligible guarantor acceptable to Morgan Stanley Dean Witter Trust FSB.
(You should contact Morgan Stanley Dean Witter Trust FSB at (800) 869-NEWS for
determination as to whether a particular institution is an eligible guarantor.) A notary public
cannot provide a signature guarantee. Additional documentation may be required for shares
held by a corporation, partnership, trustee or executor.
-------------------------------------------------------------------------------------------------
Mail the letter to Morgan Stanley Dean Witter Trust FSB at P.O. Box 983, Jersey City, NJ
07303. If you hold share certificates, you must return the certificates, along with the letter
and any required additional documentation.
-------------------------------------------------------------------------------------------------
A check will be mailed to the name(s) and address in which the account is registered, or
otherwise according to your instructions.
-----------------------------------------------------------------------------------------------------------------------
Systematic If your investment in all of the Morgan Stanley Dean Witter Family of Funds has a total
Withdrawal Plan market value of at least $10,000, you may elect to withdraw amounts of $25 or more, or in
[GRAPHIC OMITTED] any whole percentage of a fund's balance (provided the amount is at least $25), on a monthly,
quarterly, semi-annual or annual basis, from any fund with a balance of at least $1,000. Each
time you add a fund to the plan, you must meet the plan requirements.
-------------------------------------------------------------------------------------------------
To sign up for the Systematic Withdrawal Plan, contact your Morgan Stanley Dean Witter
Financial Advisor or call (800) 869-NEWS. You may terminate or suspend your plan at any
time. Please remember that withdrawals from the plan are sales of shares, not Fund
"distributions," and ultimately may exhaust your account balance. The Fund may terminate or
revise the plan at any time.
-----------------------------------------------------------------------------------------------------------------------
</TABLE>

PAYMENT FOR SOLD SHARES. After we receive your complete instructions to sell as
described above, a check will be mailed to you within seven days, although we
will attempt to make payment within one business day. Payment may also be sent
to your brokerage account.

Payment may be postponed or the right to sell your shares suspended under
unusual circumstances. If you request to sell shares that were recently
purchased by check, your sale will not be effected until it has been verified
that the check has been honored.

<PAGE>

TAX CONSIDERATIONS. Normally, your sale of Fund shares is subject to federal and
state income tax. You should review the "Tax Consequences" section of this
Prospectus and consult your own tax professional about the tax consequences of a
sale.

INVOLUNTARY SALES. The Fund reserves the right, on sixty days' notice, to sell
the shares of any shareholder (other than shares held in an IRA or 403(b)
Custodial Account) whose shares, due to sales by the shareholder, have a value
below $100, or in the case of an account opened through EasyInvestSM, if after
12 months the shareholder has invested less than $1,000 in the account.

However, before the Fund sells your shares in this manner, we will notify you
and allow you sixty days to make an additional investment in an amount that will
increase the value of your account to at least the required amount before the
sale is processed.

[GRAPHIC OMITTED]

DISTRIBUTIONS
-------------

(sidebar)
TARGETED DIVIDENDS(SM)
You may select to have your Fund distributions automatically invested in another
Morgan Stanley Dean Witter Fund that you own. Contact your Morgan Stanley Dean
Witter Financial Advisor for further information about this service.
(end sidebar)

The Fund passes substantially all of its earnings from income and capital gains
along to its investors as "distributions." The Fund earns interest from
fixed-income investments. These amounts are passed along to Fund shareholders as
"income dividend distributions." The Fund realizes capital gains whenever it
sells securities for a higher price than it paid for them. These amounts are
passed along as "capital gain distributions."

Normally, income dividends are distributed to shareholders monthly. Capital
gains, if any, are usually distributed in December. The Fund, however, may
retain and reinvest any long-term capital gains. The Fund may at times make
payments from sources other than income or capital gains that represent a return
of a portion of your investment.

Distributions are reinvested automatically in additional shares of the Fund and
automatically credited to your account, unless you request in writing that all
distributions be paid in cash. If you elect the cash option, the Fund will mail
a check to you no later than seven business days after the distribution is
declared. However, if you purchase Fund shares through a Financial Advisor
within three business days prior to the record date for the distribution, the
distribution will automatically be paid to you in cash, even if you did not
request to receive all distributions in cash. No interest will accrue on
uncashed checks. If you wish to change how your distributions are paid, your

<PAGE>

request should be received by the Fund's transfer agent, Morgan Stanley Dean
Witter Trust FSB, at least five business days prior to the record date of the
distributions.

[GRAPHIC OMITTED]

TAX CONSEQUENCES
----------------

As with any investment, you should consider how your Fund investment will be
taxed. The tax information in this Prospectus is provided as general
information. You should consult your own tax professional about the tax
consequences of an investment in the Fund.

Unless your investment in the Fund is through a tax-deferred retirement account,
such as a 401(k) plan or IRA, you need to be aware of the possible tax
consequences when:

o The Fund makes distributions; and

o You sell Fund shares, including an exchange to another Morgan Stanley Dean
Witter Fund.

TAXES ON DISTRIBUTIONS. Your distributions are normally subject to federal and
state income tax when they are paid, whether you take them in cash or reinvest
them in Fund shares. A distribution also may be subject to local income tax. Any
income dividend distributions and any short-term capital gain distributions are
taxable to you as ordinary income. Any long-term capital gain distributions are
taxable as long-term capital gains, no matter how long you have owned shares in
the Fund.

Every January, you will be sent a statement (IRS Form 1099-DIV) showing the
taxable distributions paid to you in the previous year. The statement provides
information on your dividends and capital gains for tax purposes.

TAXES ON SALES. Your sale of Fund shares normally is subject to federal and
state income tax and may result in a taxable gain or loss to you. A sale also
may be subject to local income tax. Your exchange of Fund shares for shares of
another Morgan Stanley Dean Witter Fund is treated for tax purposes like a sale
of your original shares and a purchase of your new shares. Thus, the exchange
may, like a sale, result in a taxable gain or loss to you and will give you a
new tax basis for your new shares.

When you open your Fund account, you should provide your social security or tax
identification number on your investment application. By providing this
information, you will avoid being subject to a federal backup withholding tax of
31% on taxable distributions and redemption proceeds. Any withheld amount would
be sent to the IRS as an advance tax payment.

<PAGE>

FINANCIAL HIGHLIGHTS

The financial highlights table is intended to help you understand the Fund's
financial performance for the periods indicated. Certain information reflects
financial results for a single Fund share throughout each year. The total
returns in the table represent the rate an investor would have earned or lost
on an investment in the Fund (assuming reinvestment of all dividends and
distributions).

The information for the fiscal year ended October 31, 2000 has been audited by
Deloitte & Touche LLP, independent auditors, whose report, along with the
Fund's financial statements, is included in the annual report, which is
available upon request. The financial highlights for the prior fiscal periods
have been audited by other independent accountants.

<TABLE>
<CAPTION>
FOR THE YEAR ENDED OCTOBER 31, 2000 1999 1998 1997 1996
-------------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C>
SELECTED PER-SHARE DATA
-------------------------------------------------------------------------------------------------------------------------
Net asset value, beginning of period $8.50 $8.60 $8.59 $8.39 $8.33
-------------------------------------------------------------------------------------------------------------------------
Income (loss) from investment operations:
Net investment income 0.40 0.44 0.49 0.44 0.47
Net realized and unrealized gain (loss) 0.06 (0.09) (0.05) 0.19 0.04
----- ----- ----- ----- -----
Total income from investment operations 0.46 0.35 0.44 0.63 0.51
-------------------------------------------------------------------------------------------------------------------------
Less dividends and distributions from:
Net investment income (0.36) (0.38) (0.43) (0.43) (0.45)
Paid-in-capital -- (0.07) -- -- --
----- ----- ----- ----- -----
Total dividends and distributions (0.36) (0.45) (0.43) (0.43) (0.45)
-------------------------------------------------------------------------------------------------------------------------
Net asset value, end of period $8.60 $8.50 $8.60 $8.59 $8.39
-------------------------------------------------------------------------------------------------------------------------
TOTAL RETURN+ 5.55% 4.30% 5.13% 7.80% 6.38%
-------------------------------------------------------------------------------------------------------------------------
RATIOS TO AVERAGE NET ASSETS:
-------------------------------------------------------------------------------------------------------------------------
Expenses 1.76%(1) 1.81%(1) 1.69%(1) 1.65% 1.64%
-------------------------------------------------------------------------------------------------------------------------
Net investment income 4.58% 5.11% 5.52% 5.18% 5.71%
-------------------------------------------------------------------------------------------------------------------------
SUPPLEMENTAL DATA:
-------------------------------------------------------------------------------------------------------------------------
Net assets, end of period, in thousands $91,695 $120,303 $150,441 $212,040 $350,530
-------------------------------------------------------------------------------------------------------------------------
Portfolio turnover rate -- 43% 8% -- 13%
-------------------------------------------------------------------------------------------------------------------------
</TABLE>

+ Calculated based on the net asset value as of the last business day of
the period.

(1) Does not reflect the effect of expense offset of 0.01%.

<PAGE>

NOTES

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

<PAGE>

NOTES

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

<PAGE>

MORGAN STANLEY DEAN WITTER
FAMILY OF FUNDS

The Morgan Stanley Dean Witter Family of Funds offers investors a
wide range of investment choices. Come on in and meet the family!

<TABLE>
<CAPTION>
<S> <C> <C>
-----------------------------------------------------------------------------------------------------------------------------------
GROWTH FUNDS GROWTH FUNDS THEME FUNDS
Aggressive Equity Fund Financial Services Trust
All Star Growth Fund Health Sciences Trust
American Opportunities Fund Information Fund
Capital Growth Securities Natural Resource Development Securities
Developing Growth Securities Technology Fund
Growth Fund
Market Leader Trust GLOBAL/INTERNATIONAL FUNDS
Mid-Cap Equity Trust Competitive Edge Fund - "Best Ideas" Portfolio
New Discoveries Fund European Growth Fund
Next Generation Trust Fund of Funds - International Portfolio
Small Cap Growth Fund International Fund
Special Value Fund International SmallCap Fund
Tax-Managed Growth Fund Japan Fund
21st Century Trend Fund Latin American Growth Fund
Pacific Growth Fund
-----------------------------------------------------------------------------------------------------------------------------------
GROWTH & INCOME FUNDS GROWTH & INCOME FUNDS Total Market Index Fund
Balanced Growth Fund Total Return Trust
Balanced Income Fund Value Fund
Convertible Securities Trust Value-Added Market Series/Equity Portfolio
Dividend Growth Securities
Equity Fund THEME FUNDS
Fund of Funds - Domestic Portfolio Real Estate Fund
Income Builder Fund Utilities Fund
S&P 500 Index Fund
S&P 500 Select Fund GLOBAL FUNDS
Strategist Fund Global Dividend Growth Securities
Global Utilities Fund
-----------------------------------------------------------------------------------------------------------------------------------
INCOME FUNDS GOVERNMENT INCOME FUNDS GLOBAL INCOME FUNDS
Federal Securities Trust North American Government Income Trust
Short-Term U.S. Treasury Trust World Wide Income Trust
U.S. Government Securities Trust
TAX-FREE INCOME FUNDS
DIVERSIFIED INCOME FUNDS California Tax-Free Income Fund
Diversified Income Trust Hawaii Municipal Trust(FSC)
Limited Term Municipal Trust(NL)
CORPORATE INCOME FUNDS Multi-State Municipal Series Trust(FSC)
High Yield Securities New York Tax-Free Income Fund
Intermediate Income Securities Tax-Exempt Securities Trust
Short-Term Bond Fund(NL)
-----------------------------------------------------------------------------------------------------------------------------------
MONEY MARKET FUNDS TAXABLE MONEY MARKET FUNDS TAX-FREE MONEY MARKET FUNDS
Liquid Asset Fund(MM) California Tax-Free Daily Income Trust(MM)
U.S. Government Money Market Trust(MM) New York Municipal Money Market Trust(MM)
Tax-Free Daily Income Trust(MM)
</TABLE>

There may be funds created after this Prospectus was published. Please consult
the inside back cover of a new fund's prospectus for its designations, e.g.,
Multi-Class Fund or Money Market Fund.

Unless otherwise noted, each listed Morgan Stanley Dean Witter Fund, except for
North American Government Income Trust and Short-Term U.S. Treasury Trust, is a
Multi-Class Fund. A Multi-Class Fund is a mutual fund offering multiple Classes
of shares. The other types of Funds are: NL -- No-Load (Mutual) Fund; MM --
Money Market Fund; FSC -- A mutual fund sold with a front-end sales charge and a
distribution (12b-1) fee.

<PAGE>

PROSPECTUS - DECEMBER 29, 2000

Additional information about the Fund's investments is available in the Fund's
Annual and Semi-Annual Reports to Shareholders. In the Fund's Annual Report, you
will find a discussion of the market conditions and investment strategies that
significantly affected the Fund's performance during its last fiscal year. The
Fund's Statement of Additional Information also provides additional information
about the Fund. The Statement of Additional Information is incorporated herein
by reference (legally is part of this Prospectus). For a free copy of any of
these documents to request other information about the Fund, or to make
shareholder inquiries, please call:

(800) 869-NEWS

You also may obtain information about the Fund by calling your Morgan Stanley
Dean Witter Financial Advisor or by visiting our Internet
site at:

WWW.MSDWADVICE.COM/FUNDS

Information about the Fund (including the Statement of Additional Information)
can be viewed and copied at the Securities and Exchange Commission's Public
Reference Room in Washington, DC. Information about the Reference Room's
operations may be obtained by calling the SEC at (202)942-8090. Reports and
other information about the Fund are available on the EDGAR Database on the
SEC's Internet site (www.sec.gov) and copies of this information may be
obtained, after paying a duplicating fee, by electronic request at the
following E-mail address: [email protected], or by writing the Public
Reference Section of the SEC, Washington, DC
20549-0102.

TICKER SYMBOL :

NGTVX
-----

(THE FUND'S INVESTMENT COMPANY ACT FILE NO. IS 811-6572)

MORGAN STANLEY DEAN WITTER

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

NORTH AMERICAN
GOVERNMENT INCOME TRUST

[GRAPHIC OMITTED]

A MUTUAL FUND THAT SEEKS TO
EARN A HIGH LEVEL OF CURRENT
INCOME WHILE MAINTAINING
RELATIVELY LOW VOLATILITY OF
PRINCIPAL