SHORT TERM INVESTMENTS TRUST
497, 1995-06-28
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<PAGE>
 
                         SHORT-TERM INVESTMENTS TRUST

                        TREASURY TAXADVANTAGE PORTFOLIO

                              INSTITUTIONAL CLASS


                        Supplement dated June 28, 1995
                               to the Prospectus
                          dated December 21, 1994 and
                  to the Statement of Additional Information
                            dated December 21, 1994


     Effective July 1, 1995, A I M Institutional Fund Services, Inc. ("AIFS"), a
wholly-owned subsidiary of A I M Advisors, Inc. and a registered transfer agent,
will become the exclusive transfer agent and dividend disbursing agent for the
Institutional Class (the "Class") of the Treasury TaxAdvantage Portfolio (the
"Portfolio") of Short-Term Investments Trust (the "Fund").  Since September 16,
1994, AIFS has been acting as a transfer agent for the Class providing certain
limited transfer agency services for shares of the Class.  The phone number of
AIFS is (800) 659-1005.

     AIFS will provide such transfer agency services pursuant to a Transfer
Agency and Service Agreement, dated September 16, 1994, as amended July 1, 1995,
and the Administrative Services Agreement, dated September 16, 1994, between 
A I M Advisors, Inc. and AIFS will terminate.

     Effective July 17, 1995, purchase orders and redemption requests received
by the Fund after 1:00 p.m. Eastern Time on a business day of the Portfolio will
be effected at the net asset value determined on the next business day.

     Also effective July 17, 1995: (1) the net asset value per share of the
Portfolio will be determined daily as of 1:00 p.m. Eastern Time, (2) dividends
from the net income of the Portfolio will be declared daily to shareholders of
record of the Class of the Portfolio immediately after 1:00 p.m. Eastern Time,
and (3) information concerning the amount of the dividends declared on any
particular day will normally be available by 3:30 p.m. Eastern Time on that day.
<PAGE>

SHORT-TERM
INVESTMENTS TRUST

                      Prospectus
- --------------------------------------------------------------------------------
TREASURY                The Treasury TaxAdvantage Portfolio is a money market
TAXADVANTAGE          fund whose investment objective is the maximization of
PORTFOLIO             current income to the extent consistent with the
                      preservation of capital and the maintenance of liquidity.
INSTITUTIONAL CLASS   The Treasury TaxAdvantage Portfolio seeks to achieve its
                      objective by investing in direct obligations of the U.S.
DECEMBER 21, 1994     Treasury. The Treasury TaxAdvantage Portfolio's investment
                      strategy is intended to enable the Portfolio to provide
                      its shareholders with dividends that are exempt from state
                      and local income taxation in certain jurisdictions. The
                      instruments purchased by the Treasury TaxAdvantage
                      Portfolio will have maturities of 397 days or less.

                        The Treasury TaxAdvantage Portfolio is a series
                      portfolio of Short-Term Investments Trust (the "Fund"), an
                      open-end diversified series management investment company.
                      This prospectus relates solely to the Institutional Class
                      of the Treasury TaxAdvantage Portfolio, a class of shares
                      designed to be a convenient vehicle in which institutions,
                      particularly banks, acting for themselves or in a
                      fiduciary, advisory, agency, custodial or other similar
                      capacity, can invest short-term cash reserves. The Fund
                      also offers shares of another class of the Treasury
                      TaxAdvantage Portfolio, the Private Investment Class,
                      pursuant to a separate prospectus, as well as shares of
                      classes of another portfolio, the Treasury Portfolio,
                      pursuant to separate prospectuses.

                        THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED
                      BY THE SECURITIES AND EXCHANGE COMMISSION OR ANY STATE
                      SECURITIES COMMISSION NOR HAS THE SECURITIES AND EXCHANGE
                      COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON
                      THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY
                      REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

                        THIS PROSPECTUS SETS FORTH BASIC INFORMATION THAT A
                      PROSPECTIVE INVESTOR SHOULD KNOW BEFORE INVESTING IN
                      SHARES OF THE TREASURY TAXADVANTAGE PORTFOLIO AND SHOULD
                      BE READ AND RETAINED FOR FUTURE REFERENCE. A STATEMENT OF
                      ADDITIONAL INFORMATION, DATED DECEMBER 21, 1994, HAS BEEN
                      FILED WITH THE SECURITIES AND EXCHANGE COMMISSION AND IS
                      HEREBY INCORPORATED BY REFERENCE. A COPY OF THE STATEMENT
                      OF ADDITIONAL INFORMATION, IS ATTACHED HERETO AS AN
                      APPENDIX.

                        THE FUND'S SHARES ARE NOT DEPOSITS OR OBLIGATIONS OF, OR
                      GUARANTEED OR ENDORSED BY, ANY BANK, AND THE FUND'S SHARES
                      ARE NOT FEDERALLY INSURED OR GUARANTEED BY THE U.S.
                      GOVERNMENT, THE FEDERAL DEPOSIT INSURANCE CORPORATION, THE
                      FEDERAL RESERVE BOARD OR ANY OTHER AGENCY. THERE CAN BE NO
                      ASSURANCE THAT THE TREASURY TAXADVANTAGE PORTFOLIO WILL BE
                      ABLE TO MAINTAIN A STABLE NET ASSET VALUE OF $1.00 PER
                      SHARE. SHARES OF THE fUND INVOLVE INVESTMENT RISKS,
                      INCLUDING THE POSSIBLE LOSS OF PRINCIPAL.


[AIM LOGO APPEARS HERE] 

Fund Management Company
 

11 Greenway Plaza
Suite 1919
Houston, Texas 77046-1173
(800) 659-1005

<PAGE>
 
                                    SUMMARY


THE PORTFOLIO AND ITS INVESTMENT OBJECTIVE 

  The Fund is an open-end diversified series management investment company.
Pursuant to this Prospectus, the Fund offers shares of the Institutional Class
(the "Class") of the Treasury TaxAdvantage Portfolio (the "Portfolio") without a
sales charge. The investment objective of the Portfolio is the maximization of
current income to the extent consistent with the preservation of capital and the
maintenance of liquidity. To achieve its objective, the Portfolio will invest in
direct obligations of the U.S. Treasury. The instruments purchased by the
Portfolio will have maturities of 397 days or less. The Portfolio's investment
strategy is intended to enable the Portfolio to provide its shareholders with
dividends that are exempt from state and local income taxation in certain
jurisdictions.
 
  Pursuant to a separate prospectus, the Fund offers shares of another class of
shares representing an interest in the Portfolio. Such class has a different
distribution arrangement and is designed for another category of investors. The
Fund also offers shares of several classes of the Fund representing an interest
in another portfolio, the Treasury Portfolio. The portfolios of the Fund are
referred to collectively as the "Portfolios."


INVESTORS IN THE CLASS 

  The Class is designed to be a convenient and economical investment vehicle in
which institutions, particularly banks, acting for themselves or in a fiduciary,
advisory, agency, custodial or other similar capacity, can invest short-term
cash reserves. Although shares of the Class may not be purchased by individuals
directly, institutions may purchase shares for accounts maintained by
individuals. See "Suitability for Investors." Although there is no sales charge
imposed on the purchase of shares of the Class, banks or other institutions may
charge a recordkeeping, account maintenance or other fee to their customers and
beneficial holders of the shares of the Class should consult with the
institutions maintaining their accounts to obtain a schedule of applicable fees.


PURCHASE OF SHARES 

  The shares of the Class are sold at net asset value, without a sales charge.
The minimum initial investment in the Class is $1,000,000. There is no minimum
amount for subsequent investments. Payment for shares of the Class purchased
must be in federal funds or other funds immediately available to the Portfolio.
See "Purchase of Shares."


REDEMPTION OF SHARES 

  Redemptions may be made without charge at net asset value. Payment for
redeemed shares of the Class for which redemption orders are received prior to
12:00 noon Eastern Time will normally be made in federal funds on the same day.
See "Redemption of Shares."


DIVIDENDS 

  The net income of the Portfolio is declared as a dividend daily to
shareholders of record immediately after 3:00 p.m. Eastern Time. Dividends are
paid monthly by check or wire transfer unless a shareholder has previously
elected to have such dividends automatically reinvested in additional shares of
the Class. Information concerning the amount of the dividends declared on any
particular day will normally be available by 3:30 p.m. Eastern Time on that day.
See "Dividends."


CONSTANT NET ASSET VALUE 

  The Fund uses the amortized cost method of valuing its securities held by the
Portfolio and rounds the per share net asset value to the nearest whole cent.
Accordingly, the net asset value per share of the Portfolio will normally remain
constant at $1.00. AN INVESTMENT IN THE PORTFOLIO IS NOT INSURED OR GUARANTEED
BY THE U.S. GOVERNMENT, AND THERE IS NO ASSURANCE THAT THE PORTFOLIO WILL BE
ABLE TO MAINTAIN A STABLE NET ASSET VALUE. SEE "NET ASSET VALUE."


INVESTMENT ADVISOR 

  A I M Advisors, Inc. ("AIM") serves as the Portfolio's investment advisor and
receives a fee based on the Portfolio's average daily net assets pursuant to a
master investment advisory agreement. For its services, AIM receives a fee based
on the average daily net assets of the Portfolio. During the fiscal year ended
August 31, 1994, the Portfolio paid AIM fees which represented 0.15% of the
average net assets of the Portfolio. AIM is primarily engaged in the business of
acting as manager or advisor to investment companies. See "Management of the
Fund -- Investment Advisor." Under a separate administrative services agree- 

                                       2
<PAGE>
 
ment with the Fund, AIM may receive reimbursement of its costs to perform
certain accounting and other administrative services for the Portfolio. See
"Management of the Fund -- Investment Advisor" and "-- Administrative Services."


DISTRIBUTOR 

  Fund Management Company ("FMC") acts as the exclusive distributor of the
shares of the Class. FMC does not receive any fee from the Fund. See "Purchase
of Shares."


SPECIAL RISK CONSIDERATIONS 

  The Portfolio may borrow money and enter into reverse repurchase agreements
for temporary or emergency purposes, and may purchase securities for delayed
delivery. Accordingly, an investment in the Portfolio may entail somewhat
different risks from an investment in an investment company that does not engage
in such practices. See "Investment Program."

                                       3
<PAGE>
 
                          TABLE OF FEES AND EXPENSES

<TABLE> 
<S>                                                              <C>       <C>

SHAREHOLDER TRANSACTION EXPENSES
  Maximum sales load imposed on purchases 
   (as a percentage of offering price).........................            None
  Maximum sales load on reinvested dividends 
   (as a percentage of offering price).........................            None
  Deferred sales load (as a percentage of original 
   purchase price or redemption proceeds, as applicable).......            None
  Redemption fees (as a percentage of amount 
   redeemed, if applicable)....................................            None
  Exchange fee.................................................            none
ANNUAL PORTFOLIO OPERATING EXPENSES -- INSTITUTIONAL CLASS 
(AS A PERCENTAGE OF AVERAGE NET ASSETS)
  Management fees*.............................................            0.15%
  12b-1 fees...................................................            none
  Other expenses:
    Custodian fees.............................................  0.01%
    Other......................................................  0.04%
                                                                 ----
      Total other expenses.....................................            0.05%
                                                                           ----
  Total portfolio operating expenses --
        Institutional Class....................................            0.20%
                                                                           ====
</TABLE> 
- -----------
* Had there been no fee waivers, management fees would have been 0.18%.

EXAMPLE

  An investor would pay the following expenses on a $1,000 investment, assuming
(1) a 5% annual return and (2) redemption at the end of each time period.
<TABLE> 
          <S>                                                      <C>  
           1 year...............................................   $2  
           3 years..............................................   $6
           5 years..............................................   $11
          10 years..............................................   $26
</TABLE> 
 
 
  The Table of Fees and Expenses is designed to assist an investor in
understanding the various costs and expenses that an investor in the Class will
bear directly or indirectly. For more complete descriptions of the various costs
and expenses, see "Management of the Fund" below. The expense figures are based
upon actual costs and fees charged to the Class. To the extent any service
providers assume expenses of the Class, such assumption of expenses will have
the effect of lowering the Class' overall expense ratio and increasing its yield
to investors. Beneficial owners of shares of the Class should also consider the
effect of any charges imposed by the institution maintaining their accounts.

  The example in the Table of Fees and Expenses assumes that all dividends and
distributions are reinvested and that the amounts listed under "Annual Portfolio
Operating Expenses -- Institutional Class" remain the same in the years shown.
THE EXAMPLE SHOULD NOT BE CONSIDERED TO BE AN ACCURATE REPRESENTATION OF PAST OR
FUTURE PERFORMANCE AND ACTUAL EXPENSES MAY BE GREATER OR LESS THAN THOSE SHOWN.

                                       4
<PAGE>
 
                             FINANCIAL HIGHLIGHTS

  Shown below are the per share ratios and supplemental data (collectively
"data") for the years in the four-year period ended August 31, 1994 and the
period August 17, 1990 (date operations commenced) through August 31, 1990. The
data has been audited and reported on by KPMG Peat Marwick LLP, independent
auditors, whose report on the financial statements and the related notes appears
in the Statement of Additional Information.
<TABLE> 
<CAPTION> 
                                                              August 31,
                               ------------------------------------------------------------------------
                                 1994            1993            1992            1991            1990  
                               --------        --------        --------        --------        -------- 
<S>                            <C>             <C>             <C>             <C>             <C> 

Net asset value, beginning of
 period......................  $   1.00        $   1.00        $   1.00        $   1.00        $   1.00
Income from investment
 operations:
  Net investment income......      0.03            0.03            0.04            0.07           0.003
                               --------        --------        --------        --------        -------- 
Less distributions:
  Dividends from net
   investment income.........     (0.03)          (0.03)          (0.04)          (0.07)         (0.003)
                               --------        --------        --------        --------        -------- 
Net asset value, end of 
 period......................  $   1.00        $   1.00        $   1.00        $   1.00        $   1.00
                               ========        ========        ========        ========        ========
Total return.................      3.29%           2.96%           4.32%           6.70%           7.79%(e)
                               ========        ========        ========        ========        ======== 
Ratios/supplemental data:
  Net assets, end of period
   (000s omitted)............  $403,882        $434,693        $573,283        $403,846        $ 16,201 
                               ========        ========        ========        ========        ========
  Ratio of expenses to
   average net assets........      0.20%(a,b)      0.20%           0.17%(c)        0.14%(c)        0.10%(d,e)
                               ========        ========        ========        ========        ========
  Ratio of net investment
   income to average net
   assets....................      3.23%(a,b)      2.93%           4.16%(c)        6.16%(c)        7.74%(d,e) 
                               ========        ========        ========        ========        ========
</TABLE> 
- -------------- 
(a) Based on average net assets of $431,159,563.
(b) After waiver of advisory fees. Ratio of expenses and net investment income
    to average net assets prior to waiver of advisory fees were 0.23% and 3.20%
    respectively.
(c) After waiver of advisory fees.
(d) After waiver of advisory fees and expense reimbursements.
(e) Annualized.

                                       5
<PAGE>
 
                           SUITABILITY FOR INVESTORS

  The Class is intended for use primarily by institutions, particularly banks,
acting for themselves or in a fiduciary, advisory, agency, custodial or other
similar capacity. It is designed to be a convenient and economical vehicle in
which such institutions can invest short-term cash reserves. The Portfolio's
investment strategy is intended to provide its shareholders with dividends that
are exempt from state and local income taxation in certain jurisdictions. Shares
of the Class may not be purchased directly by individuals, although institutions
may purchase shares for accounts maintained by individuals. Prospective
investors should determine if an investment in the Class is consistent with the
objectives of an account and with applicable state and federal laws and
regulations.
 
  An investment in the Class may relieve the institution of many of the
investment and administrative burdens encountered when investing in money market
instruments directly. These include: selection of portfolio investments;
surveying the market for the best price at which to buy and sell; valuation of
portfolio securities; selection and scheduling of maturities; receipt, delivery
and safekeeping of securities; and portfolio recordkeeping. It is anticipated
that most institutions will perform their own sub-accounting. To assist these
institutions, information concerning the dividends declared by the Portfolio on
any particular day will normally be available by 3:30 p.m. Eastern Time on that
day.

  Investors in the Class have the opportunity to receive a somewhat higher yield
than might be obtainable through direct investment in money market instruments,
and enjoy the benefits of same-day liquidity. Although there is no sales charge
imposed on the purchase of shares of the Class, banks or other institutions may
charge a recordkeeping, account maintenance or other fee to their customers, and
beneficial holders of the shares of the Class should consult with the
institutions maintaining their accounts to obtain a schedule of applicable fees.
Generally, higher interest rates can be obtained on the purchase of very large
blocks of money market instruments. Of course, any such relative increase in
interest rates may be offset to some extent by the operating expenses of the
Class. However, these expenses are expected to be relatively small due primarily
to the following factors: the Class will have a small number of shareholders who
do not need many of the services provided by other money market investment
companies, thereby resulting in lower transfer agent fees and costs for printing
reports and proxy statements; sales of the Class' shares to institutions acting
for themselves or in a fiduciary capacity are exempt from the registration
requirements of most state securities laws, thereby resulting in reduced state
registration fees; and the relatively low investment advisory fee paid to AIM.

  Because the Portfolio invests in direct obligations of the U.S. Treasury it
may be considered to have somewhat less risk than many other money market funds
and yields on the Portfolio may be expected to be somewhat lower than many other
money market funds. However, the possible exemption from state and local income
taxation with respect to dividends paid by the Portfolio may enable shareholders
to achieve an after-tax return comparable to or higher than that obtained from
other money market funds, which may provide an advantage to some shareholders.



                              INVESTMENT PROGRAM

INVESTMENT OBJECTIVE 

  The investment objective of the Portfolio is the maximization of current
income to the extent consistent with the preservation of capital and the
maintenance of liquidity. The Portfolio intends to provide its shareholders with
dividends that are exempt from state and local income taxation in certain
jurisdictions. The Portfolio seeks to achieve its objective by investing in
direct obligations of the U. S. Treasury. The obligations in which the Portfolio
invests are considered to carry very little risk and accordingly may not have as
high a yield as that available on instruments of lesser quality.


INVESTMENT POLICIES 

  The Portfolio invests exclusively in direct obligations of the U.S. Treasury,
which include Treasury bills, notes and bonds. The market values of the money
market instruments held by the Portfolio will be affected by changes in the
yields available on similar securities. If yields have increased since a
security was purchased, the market value of such security will generally have
decreased. Conversely, if yields have decreased, the market value of such
security will generally have increased.

  BORROWING MONEY/REVERSE REPURCHASE AGREEMENTS. The Portfolio may borrow money
and enter into reverse repurchase agreements with respect to its portfolio
securities in amounts up to 10% of the value of its total assets at the time of
borrowing or entering into a reverse repurchase agreement. The Portfolio will
only borrow money or enter into reverse repurchase agreements for temporary or
emergency purposes, such as to facilitate the orderly sale of portfolio
securities to accommodate abnormally heavy redemption requests should they
occur. Borrowing will not be made for leverage purposes. The Portfolio will use
reverse repurchase agreements when the interest income to be earned from the
securities that would otherwise have to be liquidated to meet redemption
requests is greater than the interest expense of the reverse repurchase
transaction. Reverse repurchase agreements involve the risk that the market
value of securities retained by the Portfolio in lieu of

                                       6
<PAGE>
 
liquidation may decline below the repurchase price of the securities sold by the
Portfolio which it is obligated to repurchase. The risk, if encountered, could
cause a reduction in the net asset value of the Portfolio's shares. Reverse
repurchase agreements are considered to be borrowings under the Investment
Company Act of 1940, as amended (the "1940 Act").

  PURCHASING DELAYED DELIVERY SECURITIES. In managing the Portfolio's
investments, AIM may indicate to dealers or issuers its interest in
acquiring certain securities for the Portfolio for settlement beyond a customary
settlement date. In some cases, the Portfolio may agree to purchase such
securities at stated prices and yields. In such cases, such securities are
considered "delayed delivery" securities when traded in the secondary
market. Since this is done to facilitate the acquisition of portfolio
securities and is not for the purpose of investment leverage, the amount of
delayed delivery securities involved may not exceed the estimated amount of
funds available for investment on the settlement date. Until the settlement
date, assets of the Portfolio with a dollar value sufficient at all times to
make payment for the delayed delivery securities will be segregated. The total
amount of segregated assets may not exceed 25% of the Portfolio's total assets.
The delayed delivery securities, which will not begin to accrue interest until
the settlement date, will be recorded as an asset of the Portfolio and will be
subject to the risks of market value fluctuations. The purchase price of the
delayed delivery securities will be recorded as a liability of the Portfolio
until settlement. Absent extraordinary circumstances, the Portfolio's right to
acquire delayed delivery securities will not be divested prior to the settlement
date.

  ILLIQUID SECURITIES. The Portfolio will invest no more than 10% of its net
assets in illiquid securities.

  PORTFOLIO TRANSACTIONS. The Portfolio does not seek profits through short-term
trading and will generally hold portfolio securities to maturity, but AIM may
seek to enhance the yield of the Portfolio by taking advantage of yield
disparities or other factors that occur in the money market. For example, market
conditions frequently result in similar securities trading at different
prices. AIM may dispose of any portfolio security prior to its maturity if such
disposition and reinvestment of proceeds are expected to enhance yield
consistent with AIM's judgment as to desirable portfolio maturity structure or
if such disposition is believed to be advisable due to other circumstances or
conditions. Securities held by the Portfolio will be disposed of prior to
maturity if an earlier disposition is deemed desirable by AIM to meet redemption
requests. The Portfolio's policy of investing in securities with maturities of
397 days or less will result in high portfolio turnover. Since brokerage
commissions are not normally paid on investments of the type made by the
Portfolio, however, the high turnover rate should not adversely affect the
Portfolio's net income.

  The investment policies described above may be changed by the Board of
Trustees without the affirmative vote of a majority of the outstanding shares of
the Portfolio.


INVESTMENT RESTRICTIONS 

  The Portfolio's investment program is subject to a number of investment
restrictions which reflect self-imposed standards as well as federal and state
regulatory limitations. These restrictions are designed to minimize certain
risks associated with investing in specified types of securities or engaging in
certain transactions and to limit the amount of the Portfolio's assets which may
be concentrated in any specific industry or issuer. The most significant of
these restrictions provides that the Portfolio will not:

        borrow money or issue senior securities except (a) for temporary 
        or emergency purposes (e.g., in order to facilitate the orderly 
        sale of portfolio securities to accommodate abnormally heavy 
        redemption requests), the Portfolio may borrow money from banks or 
        obtain funds by entering into reverse repurchase agreements, and 
        (b) to the extent that entering into commitments to purchase 
        securities in accordance with the Portfolio's investment program 
        may be considered the issuance of senior securities. The Portfolio  
        will not purchase securities while borrowings in excess of 5% of 
        its total assets are outstanding.

  The foregoing investment restriction of the Portfolio (as well as certain
others set forth in the Statement of Additional Information) is a matter of
fundamental policy which may not be changed without the affirmative vote of a
majority of the outstanding shares of the Portfolio.

  In addition to the restrictions described above, the Portfolio must also
comply with the requirements of Rule 2a-7 under the 1940 Act, as such Rule may
be amended from time to time, which governs the operations of money market
funds, and may be more restrictive than the policies described herein. The
Securities and Exchange Commission (the "SEC") has proposed certain changes to
Rule 2a-7. While such proposed changes may have a prospective impact on the
investments of the Portfolio, the Portfolio anticipates no difficulty in
complying with any proposed change if adopted by the SEC. A description of
further investment restrictions applicable to the Portfolio is contained in the
Statement of Additional Information.

                                       7
<PAGE>
 
                              PURCHASE OF SHARES

  Shares of the Class are sold on a continuous basis at their net asset value
next determined after an order has been accepted by the Portfolio. Although
there is no sales charge imposed on the purchase of shares of the Class, banks
or other institutions may charge a recordkeeping, account maintenance or other
fee to their customers, and beneficial holders of the shares of the Class should
consult with the institutions maintaining their accounts to obtain a schedule of
applicable fees. To facilitate the investment of proceeds of purchase orders,
investors are urged to place their orders as early in the day as possible.
Purchase orders will be accepted for execution on the day the order is placed,
provided that the order is properly submitted and received by the Portfolio
prior to 12:00 p.m. Eastern Time on a business day of the Portfolio. Purchase
orders received after such time will be processed at the next day's net asset
value. Shares of the Class will earn the dividend declared on the effective date
of purchase.

  A "business day of the Portfolio" is any day on which both the Federal Reserve
Bank of New York and The Bank of New York, the Fund's custodian, are open for
business. It is expected that The Bank of New York and the Federal Reserve Bank
of New York will be closed during the next twelve months on Saturdays and
Sundays, and on the observed holidays of New Year's Day, Martin Luther King,
Jr.'s Birthday, Presidents' Day, Memorial Day, Independence Day, Labor Day,
Columbus Day, Veterans' Day, Thanksgiving Day and Christmas Day.

  Subject to the conditions stated above and the Fund's right to reject any
purchase order, orders will be accepted (i) when payment for the shares of the
Class purchased is received by the Fund's custodian bank, in the form described
below or (ii) at the time the order is placed, if the Fund is assured of
payment. Shares of the Class purchased by orders which are accepted prior to
12:00 p.m. Eastern Time will earn the dividend declared on the date of purchase.

  Payments for shares purchased must be in the form of federal funds or other
funds immediately available to the Portfolio. Federal Reserve wires should be
sent as early as possible in order to facilitate crediting to the shareholder's
account. Any funds received with respect to an order which is not accepted by
the Portfolio and any funds received for which an order has not been received
will be returned to the sending institution.

  The minimum initial investment in the Class is $1,000,000. Institutions may be
requested to maintain separate Master Accounts in the Class for shares held by
the institution (i) for its own account, for the account of other institutions
and for accounts for which the institution acts as a fiduciary, and (ii) for
accounts for which the institution acts in some other capacity. An institution's
Master Account(s) and sub-accounts with the Class may be aggregated for the
purpose of the minimum investment requirement. No minimum amount is required for
subsequent investments in the Class nor are minimum balances required. Prior to
the initial purchase of shares of the Class, an Account Information and
Authorization Form must be completed and sent to Fund Management Company
("FMC"), 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-1173. Account
Information and Authorization Forms may be obtained from FMC. Any changes made
to the information provided in the Account Information and Authorization Form
must be made in writing or by completing a new form and providing it to FMC.

  In the interest of economy and convenience, certificates representing shares
of the Class will not be issued except upon written request to the Fund.
Certificates (in full shares only) will be issued without charge and may be
redeposited at any time.

  The Fund reserves the right in its sole discretion to withdraw all or any part
of the offering made by this Prospectus or to reject any purchase order.


                             REDEMPTION OF SHARES

  A shareholder may redeem any or all of its shares of the Class at the net
asset value next determined after receipt of the redemption request in proper
form by the Portfolio. Redemption requests with respect to the Class may also be
made via AIM LINK(TM), a personal computer application software product.
Normally, the net asset value per share of the Portfolio will remain constant at
$1.00 per share. See "Net Asset Value." Redemption requests with respect to
shares for which certificates have not been issued are normally made by calling
the Fund.

  Payment for redeemed shares is normally made by Federal Reserve wire to the
commercial bank account designated in the shareholder's Account Information and
Authorization Form, but may be remitted by check upon request by a shareholder.
If a redemption request is received by the Portfolio prior to 12:00 p.m. Eastern
Time on a business day of the Portfolio, the redemption will be effected at the
net asset value next determined on such day and the shares to be redeemed will
not receive the dividend declared on the effective date of the redemption. If a
redemption request is received by the Portfolio after 12:00 p.m. Eastern Time or
on other than a business day of the Portfolio, the redemption will be effected
at the net asset value of the Portfolio determined as of 12:00 p.m. Eastern Time
on the next business day of the Portfolio, and the proceeds of such redemption
will normally be wired on the effective day of the redemption.

                                       8
<PAGE>
 
  A shareholder may change the bank account designated to receive redemption
proceeds by written notice to the Fund. The authorized signature on the notice
must be guaranteed by a commercial bank or a trust company. Additional
documentation may be required when deemed appropriate by the Fund, State Street
Bank and Trust Company, one of the Fund's transfer agents, or AIM Institutional
Fund Services, Inc., the other transfer agent of the Fund.
 
  Payment for shares of the Class redeemed by mail and payment for telephone
redemptions in amounts under $1,000 will be made by check mailed within seven
days after receipt of the redemption request in proper form. The Fund may make
payment for telephone redemptions in excess of $1,000 by check when it is
considered to be in the Portfolio's best interest to do so.
 
  The shares of the Class are not redeemable at the option of the Fund unless
the Board of Trustees of the Fund determines in its sole discretion that failure
to so redeem may have materially adverse consequences to the shareholders of the
Fund.


                                   DIVIDENDS

  Dividends from the net income of the Portfolio are declared daily to
shareholders of record of the Class as of immediately after 3:00 p.m. Eastern
Time on the day of declaration. Net income for dividend purposes is determined
daily as of 3:00 p.m. Eastern Time. Net income of the Portfolio consists of
interest accrued and discount earned (including both original issue and market
discount) on securities held by the Portfolio, less amortization of market
premium and the accrued expenses of the Fund applicable to that dividend period
and attributable to the Portfolio. Although realized gains and losses on the
assets of the Portfolio are reflected in its net asset value, they are not
expected to be of an amount which would affect the Portfolio's net asset value
of $1.00 per share for purposes of purchases and redemptions. See "Net Asset
Value." Distributions from net realized short-term gains may be declared and
paid yearly or more frequently. See "Taxes." The Portfolio does not expect to
realize any long-term capital gains or losses.

  All dividends declared during a month will be paid by check or wire transfer.
Wire transfers may only be made in amounts of $1,000 or more. Payment will
normally be made on the first business day of the following month. A shareholder
may elect to have all dividends automatically reinvested in additional full and
fractional shares of the Portfolio at the net asset value of such shares as of
3:00 p.m. Eastern Time on the last business day of the month. Such election, or
any revocation thereof, must be made either in writing by the shareholder to FMC
at 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-1173 or transmitted via
the version of AIM LINK(TM) containing the subaccounting feature, and will
become effective with dividends paid after its receipt by FMC or, if such
election is transmitted via AIM LINK(TM), FMC's affiliates. If a shareholder
redeems all the shares of the Portfolio in its account at any time during the
month, all dividends declared through the date of redemption are paid to the
shareholder along with the proceeds of the redemption.

  The Fund uses its best efforts to maintain its net asset value per share of
the Portfolio at $1.00 for purposes of sales and redemptions. See "Net Asset
Value." Should the Fund incur or anticipate any unusual expense, loss or
depreciation which could adversely affect the income or net asset value of the
Portfolio, the Fund's Board of Trustees would at that time consider whether to
adhere to the present dividend policy described above or to revise it in light
of the then prevailing circumstances. For example, under such unusual
circumstances the Board of Trustees might reduce or suspend the daily dividend
in order to prevent to the extent possible the net asset value per share of the
Portfolio from being reduced below $1.00. Thus, such expenses, losses or
depreciation may result in a shareholder receiving no dividends for the period
during which it held its Shares and cause such a shareholder to receive upon
redemption a price per share lower than the shareholder's original cost.


                                     TAXES

FEDERAL TAXATION 

  The Fund's policy with respect to the Portfolio is to distribute to its
shareholders at least 90% of its investment company taxable income for each year
and consistent therewith to meet the distribution requirements of Part I of
Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). The
Fund intends for the Portfolio to distribute at least 98% of its net investment
income for the calendar year and at least 98% of its net realized capital gains,
if any, for the one-year period ending on October 31 and therefore to meet the
distribution requirements imposed by the Code in order to avoid the imposition
of a 4% excise tax. The Fund also intends for the Portfolio to meet the other
requirements of Subchapter M, including the requirements with respect to
diversification of assets and sources of income, so that the Portfolio will pay
no federal income taxes on net investment income and net realized capital gains
paid to shareholders.

  For purposes of determining taxable income, distribution requirements and
other requirements of Subchapter M, the Portfolio will be treated as a separate
corporation from the other portfolio comprising the Fund. Therefore, the
Portfolio may not offset its gains against losses of such other portfolio and
the Portfolio must itself specifically comply with all the provisions of the
Code.

                                       9
<PAGE>
 
  Dividends paid by the Portfolio are subject to taxation as of the date of
payment, whether received by shareholders in cash or shares of the Portfolio.
The Code provides an exception to this general rule; if the Portfolio declares a
dividend in October, November or December to shareholders of record in such
months and pays the dividend during January of the next year, a shareholder will
be treated for tax purposes as having received the dividend on December 31 of
the year in which it is declared rather than in January of the following year
when it is paid. It is anticipated that no portion of distributions will be
eligible for the dividends received deduction for corporations. Dividends paid
by the Portfolio from its net investment income and short-term capital gains are
taxable to shareholders at ordinary income tax rates.

  The foregoing discussion of federal income tax consequences is based on tax
laws and regulations in effect on the date of this Prospectus, which are subject
to change by legislation or administrative action.


STATE AND LOCAL TAXATION 

  Distributions and other Fund transactions referred to in the preceding
paragraphs may be subject to state, local or foreign taxes, and the treatment
thereof may differ from the federal income tax consequences discussed herein.
The Portfolio's investment strategy is intended to provide shareholders with
dividends that are exempt from state and local personal and, in some cases,
corporate income taxation in as many jurisdictions as possible. The possible
exemption from such taxation may enable shareholders to achieve an after-tax
return comparable to or higher than that obtained from other money market funds.
Shareholders should consult their own tax advisors concerning the tax impact of
their investment in the Portfolio and the application of state, local and
foreign taxes.


                                NET ASSET VALUE

  The net asset value per share of the Portfolio is determined daily as of 12:00
p.m. Eastern Time on each business day of the Fund. Net asset value per share is
determined by dividing the value of the Portfolio's securities, cash and other
assets (including interest accrued but not collected), less all its liabilities
(including accrued expenses and dividends payable), by the number of shares
outstanding of the Portfolio and rounding the resulting per share net asset
value to the nearest one cent.

  The securities of the Portfolio are valued on the basis of amortized cost
pursuant to rules promulgated by the Securities and Exchange Commission
applicable to money market funds. This method values a security at its cost on
the date of purchase and thereafter assumes a constant amortization to maturity
of any discount or premium, regardless of the impact of fluctuating interest
rates on the market value of the security. While this method provides certainty
in valuation, it may result in periods during which value, as determined by
amortized cost, is higher or lower than the price the Portfolio would receive if
the security were sold. During such periods, the daily yield on shares of the
Portfolio, computed as described in "Purchases and Redemptions -- Performance
Information" in the Statement of Additional Information, may differ somewhat
from an identical computation made by an investment company with identical
investments utilizing available indications as to market value to value its
portfolio securities.


                               YIELD INFORMATION

  Yield information for the Class can be obtained by calling the Fund at (800) 
659-1005. Yields will fluctuate from time to time and are not necessarily
indicative of future results. Accordingly, the yield information may not provide
a basis for comparison with investments which pay a fixed rate of interest for a
stated period of time. Yield is a function of the type and quality of the
Portfolio's investments, the Portfolio's maturity and the operating expense
ratio of the Portfolio. A SHAREHOLDER'S INVESTMENT IN THE FUND IS NOT INSURED OR
GUARANTEED BY THE U.S. GOVERNMENT OR BY ANY INSTITUTION. These factors should be
carefully considered by the investor before making an investment in the Fund.

  For the seven-day period ended August 31, 1994, the current yield and the
effective yield (which assumes the reinvestment of dividends for a 365-day year
and a return for the entire year equal to the average annualized current yield
for the period) for the Class were 4.10% and 4.18%, respectively. This yield is
quoted for illustration purposes only. The yields for any other seven-day period
may be substantially different from the yields quoted above.

  To assist banks and other institutions performing their own sub-accounting,
same day information as to the daily dividend per share for the Class to eight
decimal places and current yield normally will be available by 3:30 p.m. Eastern
Time.


                            REPORTS TO SHAREHOLDERS

  The Fund furnishes shareholders with semi-annual reports containing
information about the Portfolio and its operations, including a list of the
investments held in the Portfolio and financial statements. The annual financial
statements are audited by the Fund's independent certified public accountants. A
copy of the current list of the investments of the Portfolio will be sent to
shareholders upon request.

                                       10
<PAGE>
 
  Unless otherwise requested by the shareholder, each shareholder will be
provided with a written confirmation for each transaction. Institutions
establishing sub-accounts will receive a written confirmation for each
transaction in a sub-account. Duplicate confirmations may be transmitted to the
beneficial owner of the sub-account if requested by the institution. The
institution will receive a periodic statement setting forth, for each sub-
account, the share balance, income earned for the month, income earned for the
year to date and the total current value of the account.


                            MANAGEMENT OF THE FUND

BOARD OF TRUSTEES 

  The overall management of the business and affairs of the Fund is vested with
its Board of Trustees. The Board of Trustees approves all significant agreements
between the Fund and persons or companies furnishing services to the Fund,
including agreements with the Fund's investment advisor, distributor, custodian
and transfer agent. The day-to-day operations of the Fund are delegated to the
Fund's officers and to AIM, subject always to the objective and policies of the
Fund and to the general supervision of the Fund's Board of Trustees.


INVESTMENT ADVISOR 

  A I M Advisors, Inc., 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-
1173, acts as the investment advisor for the Portfolio pursuant to a Master
Investment Advisory Agreement dated as of October 18, 1993 (the "Advisory
Agreement"). AIM was organized in 1976 and, together with its affiliates,
manages or advises 37 investment company portfolios. As of November 3, 1994, the
total assets of the investment company portfolios managed or advised by AIM and
its affiliates were approximately $28.3 billion. All of the directors and
certain of the officers of AIM are also trustees or executive officers of the
Fund. AIM is a wholly-owned subsidiary of A I M Management Group Inc. ("AIM
Management").

  Pursuant to the terms of the Advisory Agreement, AIM manages the investment of
the Portfolio's assets and obtains and evaluates economic, statistical and
financial information to formulate and implement investment policies for the
Portfolio. The Advisory Agreement requires AIM to reduce its fee to the extent
required to satisfy any expense limitations imposed by the securities laws or
regulations thereunder of any state in which the Portfolio's shares are
qualified for sale.

  For the fiscal year ended August 31, 1994, AIM received fees from the Fund
under the Advisory Agreement with respect to the Portfolio which represented
0.15% of the Portfolio's average daily net assets. During such fiscal year, the
expenses of the Class, including AIM's fees, amounted to 0.20% of the Class'
average daily net assets.


ADMINISTRATIVE SERVICES 

  The Fund has entered into a Master Administrative Services Agreement dated as
of October 18, 1993 with AIM (the "Administrative Services Agreement"), pursuant
to which AIM has agreed to provide or arrange for the provision of certain
accounting and other administrative services to the Portfolio, including the
services of a principal financial officer of the Fund and related staff. As
compensation to AIM for its services under the Administrative Services Agreement
the Portfolio may reimburse AIM for expenses incurred by AIM in connection with
such services.

  In addition, AIM and A I M Institutional Fund Services, Inc. ("AIFS") have
entered into an Administrative Services Agreement pursuant to which AIFS is
reimbursed by AIM for its costs in providing shareholder services for the Fund.
AIFS or its affiliates received reimbursement of shareholder services costs of
$1,892 with respect to the Portfolio for the period June 1, 1994 through August
31, 1994 which represented 0.0004% of the Portfolio's average daily net assets.


FEE WAIVERS 

  AIM may in its discretion from time to time agree to waive voluntarily all or
any portion of its advisory fee and/or assume certain expenses of the Portfolio
but will retain its ability to be reimbursed prior to the end of the fiscal
year.


DISTRIBUTOR 

  The Fund has entered into a Master Distribution Agreement dated as of October
18, 1993 (the "Distribution Agreement") with FMC, a registered broker-dealer and
a wholly-owned subsidiary of AIM, to act as the exclusive distributor of the
shares of the Portfolio. The address of FMC is 11 Greenway Plaza, Suite 1919,
Houston, Texas 77046-1173. Certain trustees and officers of the Fund are
affiliated with FMC and AIM. The Distribution Agreement provides that FMC has
the exclusive right to distribute shares of the Fund either directly or through
other broker-dealers. FMC is the distributor of several of the mutual funds
managed or advised by AIM.

                                       11
<PAGE>
 
  FMC may, from time to time, at its expense, pay a bonus or other consideration
or incentive to dealers, banks or other financial institutions who sell a
minimum dollar amount of the shares of the Class during a specific period of
time. In some instances, these incentives may be offered only to certain
dealers, banks or financial institutions who have sold or may sell significant
amounts of shares. The total amount of such additional bonus payments or other
consideration shall not exceed .05% of the net asset value of the shares of the
Class sold. Any such bonus or incentive programs will not change the price paid
by investors for the purchase of shares of the Class or the amount received as
proceeds from such sales. Sales of the shares of the Class may not be used to
qualify for any incentives to the extent that such incentives may be prohibited
by the laws of any jurisdiction.


PORTFOLIO TRANSACTIONS AND BROKERAGE 

  AIM is responsible for decisions to buy and sell securities for the Portfolio,
broker-dealer selection and negotiation of commission rates. Since purchases and
sales of portfolio securities by the Portfolio are usually principal
transactions, the Portfolio incurs little or no brokerage commissions. Portfolio
securities are normally purchased directly from the issuer or from a market
maker for the securities. The purchase price paid to dealers serving as market
makers may include a spread between the bid and asked prices.

  AIM's primary consideration in effecting a security transaction is to obtain
the best net price and the most favorable execution of the order. To the extent
that the executions and prices offered by more than one dealer are comparable,
AIM may, in its discretion, effect transactions with dealers that furnish
statistical, research or other information or services which are deemed by AIM
to be beneficial to the Portfolio's investment programs. Certain research
services furnished by dealers may be useful to clients of AIM with clients other
than the Portfolio. Similarly, any research services received by AIM through
placement of portfolio transactions of other clients may be of value to AIM in
fulfilling its obligations to the Portfolio.


                              GENERAL INFORMATION

ORGANIZATION AND DESCRIPTION OF SHARES 

  The Fund is a Delaware business trust. The Fund was originally incorporated in
Maryland on January 24, 1977, but had no operations prior to November 10, 1980.
Effective December 31, 1986, the Fund was reorganized as a Massachusetts
business trust; and effective October 15, 1993, the Fund was reorganized as a
Delaware business trust. On October 15, 1993, the Portfolio succeeded to the
assets and assumed the liabilities of the Treasury TaxAdvantage Portfolio (the
"Predecessor Portfolio") of Short-Term Investments Co., a Massachusetts business
trust ("STIC"), pursuant to an Agreement and Plan of Reorganization between the
Fund and STIC. All historical financial and other information contained in this
Prospectus for periods prior to October 15, 1993 relating to the Portfolio (or a
class thereof) is that of the Predecessor Portfolio (or the corresponding class
thereof). The Fund has filed an amendment to the Registration Statement on Form
N-1A, as amended, of Short-Term Investments Co. (File No. 2-58287), pursuant to
which the Fund has expressly adopted such Registration Statement as its own
Registration Statement for all purposes of the Securities Act of 1933, as
amended, the Securities Exchange Act of 1934, as amended, and the 1940 Act.
Shares of beneficial interest of the Fund are divided into six classes of which
four represent interests in the Treasury Portfolio and two represent interests
in the Portfolio. Each class of shares has a par value of $.01 per share. All
shares of the Fund have equal rights with respect to voting, except that the
holders of shares of a particular portfolio or class will have the exclusive
right to vote on matters pertaining solely to that portfolio or class. For
example, holders of shares of a particular portfolio will have the exclusive
right to vote on any investment advisory agreement or investment restriction
that relates only to such portfolio. In addition, if a portfolio is divided into
various classes, holders of shares of a particular class will have the exclusive
right to vote on any matter, such as distribution arrangements, which relates
solely to such class. The holders of shares of the Portfolio have distinctive
rights with respect to dividends and redemption which are more fully described
in this Prospectus. In the event of liquidation or termination of the Fund,
holders of shares of each portfolio will receive pro rata, subject to the rights
of creditors, (a) the proceeds of the sale of the assets held in the respective
portfolio to which such shares relate, less (b) the liabilities of the Fund
attributable or allocated to the respective portfolio based on the liquidation
value of the portfolio. Fractional shares of each portfolio have the same rights
as full shares to the extent of their proportionate interest.

  There will not normally be annual shareholders' meetings. Shareholders may
remove trustees from office by votes cast at a meeting of shareholders called
solely for such purpose or by written consent. A meeting of shareholders for the
sole purpose of considering removal of a trustee shall be called at the request
of the holders of 10% or more of the Fund's outstanding shares.

  There are no preemptive or conversion rights applicable to any of the Fund's
shares. The Fund's shares, when issued, will be fully paid and non-assessable.
The Board of Trustees may create additional portfolios or classes of shares of
the Fund without shareholder approval.

                                       12
<PAGE>
 
TRANSFER AGENTS AND CUSTODIAN 

  The Bank of New York, 110 Washington Street, 8th Floor, New York, New York
10286, acts as custodian for the portfolio securities and cash of the Portfolio.
State Street Bank and Trust Company, 225 Franklin Street, Boston, Massachusetts
02110, acts as a transfer agent for the shares of the Class. A I M Institutional
Fund Services, Inc., 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-1173,
also acts as a transfer agent for the shares of the Class.


LEGAL COUNSEL 

  The law firm of Ballard Spahr Andrews & Ingersoll, Philadelphia, Pennsylvania,
serves as counsel to the Fund and has passed upon the legality of the shares of
the Portfolio.


SHAREHOLDER INQUIRIES 

  Shareholder inquiries concerning the status of an account should be directed
to the Fund at 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-1173, or may
be made by calling (800) 877-4744.


OTHER INFORMATION 

  This Prospectus sets forth basic information that investors should know about
the Fund and the Portfolio prior to investing. A Statement of Additional
Information has been filed with the Securities and Exchange Commission and is
attached as an Appendix to this Prospectus. Additional copies of the Statement
of Additional Information are available upon request and without charge by
writing or calling the Fund or FMC. This Prospectus omits certain information
contained in the registration statement filed with the Securities and Exchange
Commission. Copies of the registration statement, including items omitted
herein, may be obtained from the Securities and Exchange Commission by paying
the charges prescribed under its rules and regulations.

                                       13
<PAGE>
 
                     [THIS PAGE INTENTIONALLY LEFT BLANK]

                                       14
<PAGE>
 
                                   APPENDIX

                                                          STATEMENT OF
                                                          ADDITIONAL INFORMATION

                              INSTITUTIONAL CLASS

                                      OF

                        TREASURY TAXADVANTAGE PORTFOLIO

                                      OF

                         SHORT-TERM INVESTMENTS TRUST

                               11 Greenway Plaza
                                  Suite 1919
                           Houston, Texas 77046-1173
                                (800) 659-1005 
 
                                ---------------

         THIS STATEMENT OF ADDITIONAL INFORMATION IS NOT A PROSPECTUS.
             IT SHOULD BE READ IN CONJUNCTION WITH THE PROSPECTUS
                    THAT PRECEDES THIS APPENDIX, ADDITIONAL
                  COPIES OF WHICH MAY BE OBTAINED BY WRITING
                  FUND MANAGEMENT COMPANY, 11 GREENWAY PLAZA,
                     SUITE 1919, HOUSTON, TEXAS 77046-1173
                           OR CALLING (800) 659-1005
 
                                ---------------

          Statement of Additional Information dated December 21, 1994
              Relating to the Prospectus dated December 21, 1994 

                                      A-1
<PAGE>
 
                               TABLE OF CONTENTS
<TABLE> 
<S>                                                                         <C>
                                                                            PAGE
                                                                            ----
Introduction..............................................................  A-3

General Information about the Fund........................................  A-3

  The Fund and Its Shares.................................................  A-3 

  Trustees and Officers...................................................  A-5

  Investment Advisor......................................................  A-7

  Administrative Services.................................................  A-8

  Expenses................................................................  A-9

  Banking Regulations.....................................................  A-9

  Transfer Agents and Custodian...........................................  A-9

  Reports.................................................................  A-10

  Principal Holders of Securities.........................................  A-11

Purchases and Redemptions.................................................  A-14

  Net Asset Value Determination...........................................  A-14

  Distribution Agreement..................................................  A-14

  Performance Information.................................................  A-14

  Suspension of Redemption Rights.........................................  A-15

Investment Program and Restrictions.......................................  A-15

  Investment Program......................................................  A-15

  Eligible Securities.....................................................  A-15

  Investment Restrictions.................................................  A-16

  Other Investment Policies...............................................  A-17

Portfolio Transactions....................................................  A-17

Tax Matters...............................................................  A-18

  Qualification as a Regulated Investment Company.........................  A-18

  Excise Tax on Regulated Investment Companies............................  A-19

  Portfolio Distributions.................................................  A-19

  Sale or Redemption of Shares............................................  A-20

  Foreign Shareholders....................................................  A-20

  Effect of Future Legislation; State and Local Tax Considerations........  A-20

Financial Statements......................................................  FS-1
</TABLE> 
 
                                      A-2
<PAGE>
 
                                 INTRODUCTION

  The Treasury TaxAdvantage Portfolio (the "Portfolio") is an investment
portfolio of Short-Term Investments Trust (the "Fund"), a mutual fund. The rules
and regulations of the United States Securities and Exchange Commission (the
"SEC") require all mutual funds to furnish prospective investors certain
information concerning the activities of the fund being considered for
investment. This information is included in the Prospectus dated October 18,
1993 (the "Prospectus") that precedes this Statement of Additional Information.
Additional copies of the Prospectus and Statement of Additional Information may
be obtained without charge by writing the principal distributor of the Fund's
shares, Fund Management Company ("FMC"), 11 Greenway Plaza, Suite 1919, Houston,
Texas 77046-1173 or by calling (800) 659-1005. Investors must receive a
Prospectus before they invest.

  This Statement of Additional Information is intended to furnish prospective
investors with additional information concerning the Portfolio. Some of the
information required to be in this Statement of Additional Information is also
included in the Prospectus; and, in order to avoid repetition, reference will be
made to sections of the Prospectus. Additionally, the Prospectus and this
Statement of Additional Information omit certain information contained in the
registration statement filed with the SEC. Copies of the registration statement,
including items omitted from the Prospectus and this Statement of Additional
Information, may be obtained from the SEC by paying the charges prescribed under
its rules and regulations.


                      GENERAL INFORMATION ABOUT THE FUND

THE FUND AND ITS SHARES 

  The Fund is an open-end, diversified, management series investment company
which was originally organized as a corporation under the laws of the State of
Maryland on January 24, 1977, but which had no operations prior to November 10,
1980. The Fund was reorganized as a business trust under the laws of the
Commonwealth of Massachusetts on December 31, 1986. The Fund was again
reorganized as a business trust under the laws of the State of Delaware on
October 15, 1993. The Fund has filed an amendment to the Registration Statement
on Form N-1A, as amended, of Short-Term Investments Co. (File No. 2-58287),
pursuant to which the Fund has expressly adopted such Registration Statement as
its own Registration Statement for all purposes of the Securities Act of 1933,
as amended, the Securities Exchange Act of 1934, as amended, and the Investment
Company Act of 1940, as amended (the "1940 Act"). On October 15, 1993, the
Portfolio succeeded to the assets and assumed the liabilities of the Treasury
TaxAdvantage Portfolio (the "Predecessor Portfolio") of Short-Term Investments
Co., a Massachusetts business trust ("STIC"), pursuant to an Agreement and Plan
of Reorganization between the Fund and STIC. All historical financial and other
information contained in this Statement of Additional Information for periods
prior to October 15, 1993 relating to the Portfolio (or a class thereof) is that
of the Predecessor Portfolio (or the corresponding class thereof). Similarly,
the information set forth under "Principal Holders of Securities" relates to the
Predecessor Portfolios (or the corresponding classes thereof.) A copy of the
Agreement and Declaration of Trust ("Declaration of Trust") establishing the
Fund is on file with the SEC. Shares of beneficial interest of the Fund are
redeemable at the net asset value thereof at the option of the shareholder or at
the option of the Fund in certain circumstances. For information concerning the
methods of redemption and the rights of share ownership, investors should
consult the Prospectus under the captions "General Information" and "Redemption
of Shares."

  The Fund offers on a continuous basis shares representing an interest in one
of two portfolios: the Portfolio and the Treasury Portfolio (together, the
"Portfolios"). The Portfolio consists of the following two classes of shares:
Institutional Class and Private Investment Class, each pursuant to a separate
prospectus and statement of additional information. The Treasury Portfolio
consists of the following four classes of shares: Private Investment Class,
Personal Investment Class, Institutional Class and Cash Management Class. Each
such class has different shareholder qualifications and bears expenses
differently. This Statement of Additional Information and the accompanying
Prospectus relate solely to the shares of the Institutional Class (the "Class")
of the Portfolio. Shares of the Private Investment Class of the Portfolio and
the four classes of the Treasury Portfolio are offered pursuant to separate
prospectuses and statements of additional information.

  Shares of beneficial interest of the Fund will be redeemable at the net asset
value thereof at the option of the shareholder or at the option of the Fund in
certain circumstances. For information concerning the methods of redemption and
the rights of share ownership, investors should consult the Prospectus under the
caption "Redemption of Shares."

  As used in the Prospectus, the term "majority of the outstanding shares" of
the Fund, a particular portfolio or a particular class means, respectively, the
vote of the lesser of (i) 67% or more of the shares of the Fund, such portfolio
or such class present at a meeting of the Fund's shareholders, if the holders of
more than 50% of the outstanding shares of the Fund, such portfolio or such
class are present or represented by proxy, or (ii) more than 50% of the
outstanding shares of the Fund, such portfolio or such class.

                                      A-3
<PAGE>
 
  Shareholders of the Fund do not have cumulative voting rights. Therefore the
holders of more than 50% of the outstanding shares of all series or classes
voting together for election of trustees may elect all of the members of the
Board of Trustees and in such event, the remaining holders cannot elect any
members of the Board of Trustees.
 
  The Declaration of Trust provides for the perpetual existence of the Fund. The
Fund, either Portfolio and any class thereof, however, may be terminated at any
time, upon the recommendation of the Board of Trustees, by vote of a majority of
the outstanding shares of the Fund, such Portfolio and such class, respectively;
provided, however that the Board of Trustees may terminate, without such
shareholder approval, the Fund, either Portfolio and any class thereof with
respect to which there are fewer than 100 shares outstanding.

  The Declaration of Trust permits the trustees to issue an unlimited number of
full and fractional shares, of $.01 par value, of each class of shares of
beneficial interest of the Fund. The Board of Trustees may establish additional
series or classes of shares from time to time without shareholder approval.
Additional information concerning the rights of share ownership is set forth in
the prospectus applicable to each such class or portfolio of shares of the Fund.

  The assets received by the Fund for the issue or sale of shares of each class
relating to a portfolio and all income, earnings, profits, losses and proceeds
therefrom, subject only to the rights of creditors, will be allocated to that
portfolio, and constitute the underlying assets of that portfolio. The
underlying assets of each portfolio will be segregated and will be charged with
the expenses with respect to that portfolio and with a share of the general
expenses of the Fund. While certain expenses of the Fund will be allocated to
the separate books of account of each portfolio, certain other expenses may be
legally chargeable against the assets of the entire Fund.

  Under Delaware law, shareholders of a Delaware business trust shall be
entitled to the same limitations of liability extended to shareholders of
private for-profit corporations, however, there is a remote possibility that
shareholders could, under certain circumstances, be held liable for the
obligations of the Fund to the extent the courts of another state which does not
recognize such limited liability were to apply the laws of such state to a
controversy involving such obligations. However, the Declaration of Trust
disclaims shareholder liability for acts or obligations of the Fund and requires
that notice of such disclaimer be given in each agreement, obligation or
instrument entered into or executed by the Fund or the trustees to all parties,
and each party thereto must expressly waive all rights of action directly
against shareholders of the Fund. The Declaration of Trust provides for
indemnification out of the Fund's property for all losses and expenses of any
shareholder of the Fund held liable on account of being or having been a
shareholder. Thus, the risk of a shareholder incurring financial loss due to
shareholder liability is limited to circumstances in which the Fund would be
unable to meet its obligations and wherein the complaining party was held not to
be bound by the disclaimer.

  The Declaration of Trust further provides that the trustees will not be liable
for errors of judgment or mistakes of fact or law. However, nothing in the
Declaration of Trust protects a trustee against any liability to which a trustee
would otherwise be subject by reason of willful misfeasance, bad faith, gross
negligence, or reckless disregard of the duties involved in the conduct of his
office. The Declaration of Trust provides for indemnification by the Fund of the
trustees and the officers of the Fund except with respect to any matter as to
which any such person did not act in good faith in the reasonable belief that
his action was in or not opposed to the best interests of the Fund. Such person
may not be indemnified against any liability to the Fund or to the Fund's
shareholders to which he would otherwise be subject by reason of willful
misfeasance, bad faith, gross negligence or reckless disregard of the duties
involved in the conduct of his office. The Declaration of Trust also authorizes
the purchase of liability insurance on behalf of trustees and officers.

  As described in the Prospectus, the Fund will not normally hold annual
shareholders' meetings. At such time as less than a majority of the trustees
have been elected by the shareholders, the trustees then in office will call a
shareholders' meeting for the election of trustees. In addition, trustees may be
removed from office by a written consent signed by the holders of two-thirds of
the outstanding shares of the Fund and filed with the Fund's custodian or by a
vote of the holders of two-thirds of the outstanding shares at a meeting duly
called for the purpose, which meeting shall be held upon written request of the
holders of not less than 10% of the outstanding shares of the Fund.

                                      A-4
<PAGE>
 
TRUSTEES AND OFFICERS 

  The trustees and officers of the Fund and their principal occupations during
the last five years are set forth below. Unless otherwise indicated, the address
of each trustee and officer is 11 Greenway Plaza, Suite 1919, Houston, Texas
77046-1173.

  *CHARLES T. BAUER, Trustee and Chairman 

     Director and Chairman and Chief Executive Officer, A I M Management Group
   Inc.; Chairman of the Board of Directors, A I M Advisors, Inc., A I M Capital
   Management, Inc., A I M Distributors, Inc., A I M Fund Services, Inc., A I M
   Institutional Fund Services, Inc. and Fund Management Company.

   BRUCE L. CROCKETT, Trustee  
   COMSAT Corporation 
   6560 Rock Spring Drive  
   Bethesda, MD 20817 

     Director, President and Chief Executive Officer, COMSAT Corporation
   (Includes COMSAT World Systems, COMSAT Mobile Communications, COMSAT Video
   Enterprises, COMSAT RSI and COMSAT International Ventures). Previously,
   President and Chief Operating Officer, COMSAT Corporation; President, World
   Systems Division, COMSAT Corporation; and Chairman, Board of Governors of
   INTELSAT (each of the COMSAT companies listed above is an international
   communication, information and entertainment distribution services company).
 
   OWEN DALY II, Trustee  
   Six Blythewood Road  
   Baltimore, MD 21210 
 
     Director, Cortland Trust Inc. (investment company). Formerly, Director, 
   CF & I Steel Corp., Monumental Life Insurance Company and Monumental General
   Insurance Company; and Chairman of the Board of Equitable Bancorporation.

 **CARL FRISCHLING, Trustee 
   919 Third Avenue 
   New York, NY 10022 

     Partner, Kramer, Levin, Naftalis, Nessen, Kamin & Frankel (law firm).
   Formerly, Partner, Reid & Priest (law firm); and, prior thereto, Partner,
   Spengler Carlson Gubar Brodsky & Frischling (law firm).
 
  *ROBERT H. GRAHAM, Trustee and President 
   
     Director, President and Chief Operating Officer, A I M Management Group
   Inc.; Director and President, A I M Advisors, Inc.; Director and Executive
   Vice President, A I M Distributors, Inc.; Director and Senior Vice President,
   A I M Institutional Fund Services, Inc. and Fund Management Company; and
   Director and Vice President, A I M Capital Management, Inc., and A I M 
   Fund Services, Inc.

   JOHN F. KROEGER, Trustee  
   Box 464  
   24875 Swan Road-Martingham  
   St. Michaels, MD 21663 

     Trustee, Flag Investors International Trust; and Director, Flag Investors
   Emerging Growth Fund, Inc., Flag Investors Telephone Income Fund, Inc., Flag
   Investors Quality Growth Fund, Inc., Flag Investors Total Return U.S.
   Treasury Fund, Inc., Flag Investors Intermediate Term Income Fund, Inc.,
   Managed Municipal Fund, Inc., Flag Investors Value Builder Fund, Inc., Flag
   Investors Maryland Intermediate Tax-Free Income Fund, Inc., Alex. Brown Cash
   Reserve Fund, Inc. and North American Government Bond Fund, Inc. (investment
   companies). Formerly, Consultant, Wendell & Stockel Associates, Inc.
   (consulting firm).
- ------------
 *A trustee who is an "interested person" of the Fund and AIM, as defined in 
  the 1940 Act.
**A trustee who is an "interested person" of the Fund, as defined in the 1940 
  Act.

                                      A-5
<PAGE>
 
   LEWIS F. PENNOCK, Trustee  
   8955 Katy Freeway, Suite 204  
   Houston, TX 77024 

     Attorney in private practice in Houston, Texas.
 
   IAN W. ROBINSON, Trustee  
   183 River Drive  
   Tequesta, FL 33469 
 
     Formerly, Executive Vice President and Chief Financial Officer, Bell
   Atlantic Management Services, Inc. (provider of centralized management
   services to telephone companies); Executive Vice President, Bell Atlantic
   Corporation (parent of seven telephone companies); and Vice President and
   Chief Financial Officer, Bell Telephone Company of Pennsylvania and Diamond
   State Telephone Company.

   LOUIS S. SKLAR, Trustee  
   Transco Tower, 50th Floor  
   2800 Post Oak Blvd.  
   Houston, TX 77056 

     Executive Vice President, Development and Operations, Hines Interests
   Limited Partnership (real estate development).
 
   WILLIAM H. KLEH, Senior Vice President 
 
     Director and Senior Vice President, A I M Advisors, Inc.; Director and Vice
   President, Fund Management Company; Senior Vice President, A I M Management
   Group Inc.; and Vice President, A I M Capital Management, Inc., A I M
   Distributors, Inc. and A I M Fund Services, Inc.

   JOHN J. ARTHUR, Senior Vice President and Treasurer 

     Senior Vice President and Treasurer, A I M Advisors, Inc.; and Vice
   President and Treasurer, A I M Management Group Inc., A I M Capital
   Management, Inc., A I M Distributors, Inc., A I M Fund Services, Inc., A I M
   Institutional Fund Services Inc. and Fund Management Company.

   GARY T. CRUM, Senior Vice President 

     Director and President, A I M Capital Management, Inc.; Director and Senior
   Vice President, A I M Management Group Inc. and A I M Advisors, Inc.; and
   Director, A I M Distributors, Inc.

   CAROL F. RELIHAN, Vice President and Secretary 

     Vice President, General Counsel and Secretary, A I M Advisors, Inc., A I M
   Distributors, Inc., A I M Institutional Fund Services, Inc., A I M Fund
   Services, Inc., A I M Management Group Inc. and Fund Management Company; and
   General Counsel and Secretary, A I M Capital Management, Inc.

   DANA R. SUTTON, Vice President and Assistant Treasurer 

     Vice President and Fund Controller, A I M Advisors, Inc.; and Assistant
   Vice President and Assistant Treasurer, Fund Management Company.

   POLLY A. AHRENDTS, Vice President 

     Vice President, A I M Capital Management, Inc.

   GARY V. BEAUCHAMP, Vice President 

     Vice President, A I M Capital Management, Inc.

   MELVILLE B. COX, Vice President 

     Vice President, A I M Advisors, Inc., A I M Capital Management, Inc., A I M
   Institutional Fund Services, Inc. and A I M Fund Services, Inc.; and
   Assistant Vice President, A I M Distributors, Inc. and Fund Management
   Company. Formerly, Vice President, Charles Schwab & Co., Inc.; Assistant
   Secretary, Charles Schwab Family of Funds and Schwab Investments; Chief
   Compliance Officer, Charles Schwab Investment Management, Inc.; and Vice
   President, Integrated Resources Life Insurance Co. and Capitol Life Insurance
   Co.

                                      A-6
<PAGE>
 
   KAREN DUNN KELLEY, Vice President 

     Senior Vice President, A I M Capital Management, Inc.; and Vice President, 
   A I M Advisors, Inc.

   J. ABBOTT SPRAGUE, Vice President 

     Director and President, A I M Institutional Fund Services, Inc. and Fund
   Management Company; Director and Senior Vice President, A I M Advisors, Inc.;
   and Senior Vice President, A I M Fund Services, Inc. and A I M Management
   Group Inc.

  The members of the Audit Committee are Messrs. Daly, Kroeger, Pennock and
Robinson. The Audit Committee is responsible for meeting with the Fund's
auditors to review audit procedures and results and to consider any matters
arising from an audit to be brought to the attention of the trustees as a whole
with respect to the Fund's fund accounting or its internal accounting controls,
or for considering such matters as may from time to time be set forth in a
charter adopted by the Board of Trustees and such committee.

  The members of the Investments Committee are Messrs. Bauer, Crockett, Daly,
Kroeger and Pennock. The Investments Committee is responsible for reviewing
portfolio compliance, brokerage allocation, portfolio investment pricing issues,
interim dividend and distribution issues, or considering such matters as may
from time to time be set forth in a charter adopted by the Board of Trustees and
such committee.

  The members of the Nominating and Compensation Committee are Messrs. Crockett,
Daly, Kroeger, Pennock and Sklar. The Nominating and Compensation Committee is
responsible for considering and nominating individuals to stand for election as
trustees who are not interested persons as long as the Fund maintains a
distribution plan pursuant to Rule 12b-1 under the 1940 Act, reviewing from time
to time the compensation payable to the disinterested trustees, or considering
such matters as may from time to time be set forth in a charter adopted by the
Board of Trustees and such committee.

  All of the Fund's trustees also serve as directors or trustees of some or all
of the other investment companies managed or advised by A I M Advisors, Inc.
("AIM") or distributed and administered by FMC. All of the Fund's executive
officers hold similar offices with some or all of such investment companies.

  Each trustee is reimbursed for expenses incurred in connection with each
meeting of the Board of Trustees or any Committee attended. The trustees of the
Trust who do not serve as officers of the Trust are compensated for their
services according to a fee schedule which recognizes the fact that they also
serve as directors or trustees of certain other investment companies advised or
managed by AIM. Each such trustee receives a fee, allocated among the investment
companies for which he serves as a director or trustee, which consists of two
components: (i) an annual retainer, based on the number of series portfolios of
the investment companies for which such trustee serves as director/trustee
("Series"), which annual retainer shall equal the sum of $7,500 for the first
Series, $5,000 for the second Series, $2,500 for the third Series, $1,000 for
each of the fourth through tenth Series, and $750 for each additional Series,
with 50% of such annual retainer being allocated equally among the Series for
which the trustee serves as director/trustee, and 50% of such annual retainer
being allocated among the Series based upon their relative net assets; and (ii)
a meeting fee of $250 per Series, up to a maximum of $1,000 per meeting, for
each board meeting attended in person by such trustee, with 50% of such meeting
fee being allocated equally among the Series for which the trustee serves as
director/trustee, and 50% allocated among the Series based upon their relative
net assets.

  During the fiscal year ended August 31, 1994, the Fund paid $8,407 and $32,897
in trustees' fees and expenses allocated to the Portfolio and the Treasury
Portfolio, respectively.

  The Fund paid Reid & Priest $6,735 in legal fees for services provided to the
Portfolio during the fiscal year ended August 31, 1994. Carl Frischling,
Esquire, trustee to the Fund was a partner in such firm.


INVESTMENT ADVISOR 

  A I M Advisors, Inc., 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-
1173, acts as the investment advisor of the Portfolio pursuant to a Master
Investment Advisory Agreement dated as of October 18, 1993 (the "Advisory
Agreement"). AIM was organized in 1976, and together with its affiliates advises
or manages 37 investment company portfolios. As of November 3, 1994, the total
assets of the investment company portfolios managed or advised by AIM and its
affiliates were approximately $28.3 billion.

  Pursuant to the terms of the Advisory Agreement, AIM manages the investment of
the assets of the Portfolio. AIM obtains and evaluates economic, statistical and
financial information to formulate and implement investment policies for the
Portfolio. Any investment program undertaken by AIM will at all times be subject
to the policies and control of the Fund's Board of Trust 

                                      A-7
<PAGE>
 
ees. AIM shall not be liable to the Fund or to its shareholders for any act or
omission by AIM or for any loss sustained by the Fund or its shareholders except
in the case of willful misfeasance, bad faith, gross negligence or reckless
disregard of duty.

  As compensation for its services with respect to the Portfolio, AIM receives a
monthly fee which is calculated by applying the following annual rates to the
average daily net assets of the Portfolio:

                        Net Assets                           Rate  
                        ----------                           ----
            First $250 million                               .20%

            Over $250 million to $500 million                .15%

            Over $500 million                                .10%

The Advisory Agreement requires AIM to reduce its fee to the extent required
to satisfy any expense limitations imposed by the securities laws or regulations
thereunder of any state in which the Portfolio's shares are qualified for sale.

  Pursuant to an investment advisory agreement between the Fund and AIM,
previously in effect with respect to the Portfolio, which provided for the same
level of compensation to AIM as the Agreement, AIM received fees (net of fee
waivers, if any) from the Fund for the fiscal years ended August 31, 1994, 1993
and 1992, with respect to the Portfolio in the amounts of $640,698, $904,014 and
$714,988, respectively. For the fiscal years ended August 31, 1994, 1993 and
1992, AIM waived fees with respect to the Portfolio in the amounts of $131,042,
$0 and $154,233, respectively.

  The Advisory Agreement provides, that, upon the request of the Board of
Trustees, AIM may perform or arrange for the performance of certain additional
services on behalf of the Portfolio which are not required by the Advisory
Agreement. AIM may receive reimbursement or reasonable compensation for certain
additional services, as may be agreed upon by AIM and the Board of Trustees,
based upon a finding by the Board of Trustees that the provision of such
services would be in the best interest of the Portfolio and its shareholders.
The Board of Trustees has made such a finding and, accordingly, has entered into
a master administrative services agreement under which AIM will provide the
additional services described below under the caption "Administrative Services."

  The Advisory Agreement was approved for its initial term by the Board of
Trustees on July 19, 1993. The Advisory Agreement will continue in effect until
June 30, 1995 and from year to year thereafter provided that it is specifically
approved at least annually by the Fund's Board of Trustees and the affirmative
vote of a majority of the trustees who are not parties to the Advisory Agreement
or "interested persons" of any such party by votes cast in person at a meeting
called for such purpose. The Fund or AIM may terminate the Advisory Agreement on
60 days' notice without penalty. The Advisory Agreement terminates automatically
in the event of its assignment, as defined in the 1940 Act.

  AIM is a wholly-owned subsidiary of A I M Management Group Inc. ("AIM
Management"), 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-1173. All of
the directors and certain of the officers of AIM are also executive officers of
the Fund and their affiliations are shown under "Trustees and Officers." The
address of each director and officer of AIM is 11 Greenway Plaza, Suite 1919,
Houston, Texas 77046.

  FMC is a registered broker-dealer and a wholly-owned subsidiary of AIM. FMC
acts as distributor of the shares of the Class.


ADMINISTRATIVE SERVICES 

  AIM also provides certain services pursuant to a Master Administrative
Services Agreement dated as of October 18, 1993 between AIM and the Fund (the
"Administrative Services Agreement"). In addition, AIM and A I M Institutional
Fund Services, Inc. ("AIFS") have entered into an Administrative Services
Agreement, dated as of September 16, 1994 (the "AIFS Administrative Services
Agreement").

  Under the Administrative Services Agreement, AIM performs accounting and other
administrative services for the Portfolio. As full compensation for the
performance of such services, AIM is reimbursed for any personnel and other
costs (including applicable office space, facilities and equipment) of
furnishing the services of a principal financial officer of the Fund and of
persons working under his supervision for maintaining the financial accounts and
books and records of the Fund, including calculation of the Portfolio's daily
net asset value, and preparing tax returns and financial statements for the
Portfolio. The method of calculating such reimbursements must be annually
approved, and the amounts paid will be periodically reviewed, by the Fund's
Board of Trustees.

  The Administrative Services Agreement was initially approved by the Board of
Trustees on July 19, 1993. Pursuant to an administrative services agreement
between the Fund and AIM, previously in effect, which provided for the same
level of reimbursement to AIM as the Administrative Services Agreement, AIM was
reimbursed for the fiscal years ended August 31, 1994, 1993 and 1992, in the
amounts of $31,534, $29,382 and $27,765, respectively, for fund accounting
services for the Portfolio.

                                      A-8
<PAGE>
 
  The AIFS Administrative Services Agreement between AIM and AIFS, a registered
transfer agent and wholly-owned subsidiary of AIM, provides that AIFS may
perform certain shareholder services for the Fund. For such services, AIFS is
entitled to receive from AIM such reimbursement of its costs associated with
each such Fund as may be approved by the Fund's Board of Trustees. For the
period from June 1, 1994 through August 31, 1994, AIFS or its affiliates
received shareholder services fees with respect to the Portfolio in the amount
of $1,892.


EXPENSES 

  In addition to fees paid to AIM pursuant to the Agreement and the expenses
reimbursed to AIM under the Administrative Services Agreement, the Fund also
pays or causes to be paid all other expenses of the Fund, including, without
limitation: the charges and expenses of any registrar, any custodian or
depository appointed by the Fund for the safekeeping of its cash, portfolio
securities and other property, and any transfer, dividend or accounting agent or
agents appointed by the Fund; brokers' commissions chargeable to the Fund in
connection with portfolio securities transactions to which the Fund is a party;
all taxes, including securities issuance and transfer taxes, and fees payable by
the Fund to federal, state or other governmental agencies; the costs and
expenses of engraving or printing of certificates representing shares of the
Fund; all costs and expenses in connection with the registration and maintenance
of registration of the Fund and its shares with the SEC and various states and
other jurisdictions (including filing and legal fees and disbursements of
counsel); the costs and expenses of printing, including typesetting, and
distributing prospectuses and statements of additional information of the Fund
and supplements thereto to the Fund's shareholders; all expenses of
shareholders' and trustees' meetings and of preparing, printing and mailing of
prospectuses, proxy statements and reports to shareholders; fees and travel
expenses of trustees and trustee members of any advisory board or committee; all
expenses incident to the payment of any dividend, distribution, withdrawal or
redemption, whether in shares or in cash; charges and expenses of any outside
service used for pricing of the Fund's shares; charges and expenses of legal
counsel, including counsel to the trustees of the Fund who are not "interested
persons" (as defined in the 1940 Act) of the Fund or AIM, and of independent
accountants in connection with any matter relating to the Fund; membership dues
of industry associations; interest payable on Fund borrowings; postage;
insurance premiums on property or personnel (including officers and trustees) of
the Fund which inure to its benefit; and extraordinary expenses (including, but
not limited to, legal claims and liabilities and litigation costs and any
indemnification related thereto). FMC bears the expenses of printing and
distributing prospectuses and statements of additional information (other than
those prospectuses and statements of additional information distributed to
existing shareholders of the Fund) and any other promotional or sales literature
used by FMC or furnished by FMC to purchasers or dealers in connection with the
public offering of the Fund's shares.

  Expenses of the Fund which are not directly attributable to the operations of
any class of shares or portfolio of the Fund are prorated among all classes of
the Fund based upon the relative net assets of each class. Expenses of the Fund
which are not directly attributable to a specific class of shares but are
directly attributable to a specific portfolio are prorated among all classes of
such portfolio based upon the relative net assets of each such class. Expenses
of the Fund which are directly attributable to a specific class of shares are
charged against the income available for distribution as dividends to the
holders of such shares.


BANKING REGULATIONS 

  The Glass-Steagall Act and other applicable laws, among other things,
generally prohibit federally chartered or supervised banks from engaging in the
business of underwriting, selling or distributing securities, but permit banks
to make shares of mutual funds available to their customers and to perform
administrative and shareholder servicing functions. However, judicial or
administrative decisions or interpretations of such laws, as well as changes in
either federal or state statutes or regulations relating to the permissible
activities of banks or their subsidiaries or affiliates, could prevent a bank
from continuing to perform all or a part of its servicing activities. If a bank
were prohibited from so acting, shareholder clients of such bank would be
permitted to remain shareholders of the Fund and alternate means for continuing
the servicing of such shareholders would be sought. In such event, changes in
the operation of the Fund might occur and shareholders serviced by such bank
might no longer be able to avail themselves of any automatic investment or other
services then being provided by such bank. It is not expected that shareholders
would suffer any adverse financial consequences as a result of any of these
occurrences. In addition, state securities laws on this issue may differ from
the interpretations of federal law expressed herein and certain banks and
financial institutions may be required to register as dealers pursuant to state
law.


TRANSFER AGENTS AND CUSTODIAN 

  The Bank of New York acts as custodian for the portfolio securities and cash
of the Portfolio. The Bank of New York receives such compensation from the Fund
for its services in such capacity as is agreed to from time to time by The Bank
of New York and the Fund. The address of The Bank of New York is 110 Washington
Street, 8th Floor, New York, New York 10286.

                                      A-9
<PAGE>
 
  State Street Bank and Trust Company serves as a transfer agent for the shares
of the Class and receives such compensation from the Fund for its services in
such capacity as is agreed to from time to time by State Street Bank and Trust
Company and the Fund. The address of State Street Bank and Trust Company is 225
Franklin Street, Boston, Massachusetts 02110. A I M Institutional Fund Services,
Inc., 11 Greenway Plaza, Suite 1919, Houston, Texas 77046-1173, also acts as a
transfer agent for the shares of the Class.


REPORTS 

  The Fund furnishes shareholders with semi-annual reports containing
information about the Fund and its operations, including a schedule of
investments held in the Portfolio and its financial statements. The annual
financial statements are audited by the Fund's independent auditors. The Board
of Trustees has selected KPMG Peat Marwick LLP, NationsBank Building, 700
Louisiana, Houston, Texas 77002, as the independent auditors to audit the
financial statements and review the tax returns of the Portfolio.

                                     A-10
<PAGE>
 
PRINCIPAL HOLDERS OF SECURITIES 

TREASURY PORTFOLIO 

  To the best of the knowledge of the Fund, the names and addresses of the
holders of 5% or more of the outstanding shares of any class of the Treasury
Portfolio as of October 31, 1994, and the percentage of such shares owned by
such shareholders as of such date are as follows:

INSTITUTIONAL CLASS  
- -------------------

<TABLE> 
<CAPTION> 
                                                                  PERCENT
                      NAME AND ADDRESS                            OWNED OF
                      OF RECORD OWNER                          RECORD ONLY(a)
                      ----------------                         --------------
     <S>                                                       <C>
     NationsBank of Texas, N.A...............................      20.71%
      1401 Elm Street, 11th Floor 
      Dallas, TX 75202-2911

     Wachovia Bank of North Carolina.........................      11.77%
      Trust Operations 
      P.O. Box 3075 MC 
      Winston-Salem, NC 31051

     Trust Company of Georgia................................      11.70%
      P.O. Box 105213 
      Atlanta, GA 30348

     Texas Commerce Bank.....................................       7.39%
      601 Travis 
      Houston, TX 77002

     Victoria & Co...........................................       6.27%
      Trust Operations 
      P.O. Box 1698 
      Victoria, TX 77902

     U.S. Bank of Washington.................................       6.26%
      Trust Securities 
      1414 Fourth Avenue 
      Seattle, WA 98111
</TABLE> 
 
PERSONAL INVESTMENT CLASS  
- -------------------------
<TABLE>
<CAPTION> 
                                                                 PERCENT
                      NAME AND ADDRESS                           OWNED OF
                      OF RECORD OWNER                           RECORD ONLY
                      ----------------                          -----------
     <S>                                                        <C>
     Republic National Bank of New York......................      48.59%(a,b)  
      1 Hanson Place, Lower 
      Brooklyn, NY 11243

     Frost National Bank.....................................      47.41%(b,c) 
      P.O. Box 1600 
      San Antonio, TX 78296
</TABLE> 
- ---------------
(a)  The Fund has no knowledge as to whether all or any portion of the shares 
     owned of record only are also owned beneficially.

(b)  A shareholder who holds 25% or more of the outstanding shares of a class
     may be presumed to be in "control" of such class of shares, as defined in
     the 1940 Act.

(c)  The Fund has knowledge as to certain shares beneficially owned, however to
     the best knowledge of the Fund, no one beneficially owns 5% or more of the
     outstanding shares of the class.

                                     A-11
<PAGE>
 
PRIVATE INVESTMENT CLASS  
- ------------------------
<TABLE> 
<CAPTION> 
                                                                 PERCENT
                      NAME AND ADDRESS                           OWNED OF
                      OF RECORD OWNER                           RECORD ONLY
                      ----------------                          -----------
     <S>                                                        <C>
     VAR & Co. ..............................................      32.17%(a,b)
      180 East 5th Street 
      St. Paul, MN 55101 

     Liberty Bank and Trust Company of Tulsa, N.A............      31.70%(a,b)
      P.O. Box 25848 
      Tulsa, OK 74101 

     Huntington Capital......................................      19.35%(c)
      41 South High Street 
      Columbus, OH 43287 

     CoreStates Bank, N.A....................................      11.22%(a)
      Penn Mutual Insurance Building 
      530 Walnut Street 
      Philadelphia, PA 19106 
</TABLE> 
  
CASH MANAGEMENT CLASS  
- ---------------------
<TABLE> 
<CAPTION> 
                                                   PERCENT        PERCENT
                 NAME AND ADDRESS                   OWNED         OWNED OF
                 OF RECORD OWNER              BENEFICIALLY ONLY  RECORD ONLY
                 ----------------             -----------------  -----------
     <S>                                      <C>                <C>
     United Counties Trust Company..........       - 0 -           25.16%(a,b)  
      30 Maple Street 
      Summit, NJ 07901 

     City of Burbank........................        9.44%          - 0 -
      333 South Beaudry Avenue, 25th Floor 
      Los Angeles, CA 95691 

     Montgomery County......................        7.80%          - 0 -
      101 Monrose Street, 15th Floor 
      Rockville, MD 20850  

     City of Ontario........................        6.07%          - 0 -
      303 East "B" Street 
      Ontario, CA 91764 

     City of Beaumont-Meridian Trust Company 
      of California.........................        5.86%          - 0 -
      35 North 6th Street 
      Reading, PA 19603 

     City of West Sacramento................        5.80%          - 0 -
      2101 Stone Boulevard 
      West Sacramento, CA 95691 
</TABLE> 
- ---------------
(a)  The Fund has no knowledge as to whether all or any portion of the shares 
     owned of record only are also owned beneficially.

(b)  A shareholder who holds 25% or more of the outstanding shares of a class 
     may be presumed to be in "control" of such class of shares, as defined in 
     the 1940 Act.

(c)  The Fund has knowledge as to certain shares beneficially owned, however 
     to the best knowledge of the Fund, no one beneficially owns 5% or more of 
     the outstanding shares of the class.

                                     A-12
<PAGE>
 
TREASURY TAXADVANTAGE PORTFOLIO 

  To the best of the knowledge of the Fund, the names and addresses of the
holders of 5% or more of the outstanding shares of any class of the Treasury
TaxAdvantage Portfolio as of October 31, 1994, and the percentage of such shares
owned by such shareholders as of such date are as follows:

INSTITUTIONAL CLASS
- -------------------
<TABLE> 
<CAPTION> 
                                                                  PERCENT
                      NAME AND ADDRESS                            OWNED OF
                      OF RECORD OWNER                          RECORD ONLY(a)
                      ----------------                         --------------
     <S>                                                       <C>
     FirsTier Bank Omaha.....................................      26.87%(b)  
      1700 Farnam Street 
      Omaha, NE 68102

     Muchmore & Co...........................................      19.03%
      P.O. Box 1205 
      Cranford, NJ 07016

     First National Bank of Maryland.........................       8.69%
      P.O. Box 1596 
      Baltimore, MD 21203

     Sanwa Bank..............................................       5.75%
      P.O. Box 60078 
      Los Angeles, CA 90060

     Wachovia Bank of North Carolina.........................       5.21%
      P.O. Box 3075 
      Winston-Salem, NC 27150

     Liberty Bank and Trust Company, N.A.....................       5.09%
      P.O. Box 25848 
      Oklahoma City, OK 73125

     Boatmen's Trust Company.................................       5.03%
      100 North Broadway 
      St. Louis, MO 63101 
</TABLE> 
    
PRIVATE INVESTMENT CLASS
- ------------------------ 

  AIM provided the initial capitalization of the Private Investment Class of the
Treasury TaxAdvantage Portfolio and, accordingly, as of the date of this
Statement of Additional Information, owned all the outstanding shares of
beneficial interest of the Private Investment Class of the Treasury TaxAdvantage
Portfolio. Although the Private Investment Class of the Treasury TaxAdvantage
Portfolio expects that the sale of its shares to the public pursuant to the
Prospectus will promptly reduce the percentage of such shares owned by AIM to
less than 1% of the total shares outstanding, as long as AIM owns over 25% of
the shares of the Private Investment Class of the Treasury TaxAdvantage
Portfolio that are outstanding, it may be presumed to be in "control" of the
Private Investment Class of the Treasury TaxAdvantage Portfolio, as defined in
the 1940 Act.

  Shares shown as beneficially owned by the above institutions are those shares
for which the institutions possessed or shared voting or investment power with
respect to such shares on behalf of their underlying accounts.

  To the best of the knowledge of the Fund, as of October 31, 1994, the trustees
and officers of the Fund beneficially owned less than 1% of each class of the
Fund's outstanding shares.
- ---------------
(a)  The Fund has no knowledge as to whether all or any portion of the shares 
     owned of record only are also owned beneficially.

(b)  A shareholder who holds 25% or more of the outstanding shares of a class 
     may be presumed to be in "control" of such class of shares, as defined in
     the 1940 Act.

                                     A-13
<PAGE>
 
                           PURCHASES AND REDEMPTIONS

NET ASSET VALUE DETERMINATION 

  Shares of the Class are sold at the net asset value of such shares.
Shareholders may at any time redeem all or a portion of their shares at net
asset value. The investor's price for purchases and redemptions will be the net
asset value next determined following the receipt of an order to purchase or a
request to redeem shares.

  The valuation of the portfolio instruments based upon their amortized cost and
the concomitant maintenance of the net asset value per share of $1.00 for the
Portfolio is permitted in accordance with applicable rules and regulations of
the SEC, including Rule 2a-7, which require the Fund to adhere to certain
conditions. These rules require that the Fund maintain a dollar-weighted average
portfolio maturity of 90 days or less for the Portfolio, purchase only
instruments having remaining maturities of 397 days or less and invest only in
securities determined by the Board of Trustees to be of high quality with
minimal credit risk.

  The Board of Trustees is required to establish procedures designed to
stabilize, to the extent reasonably practicable, the Fund's price per share at
$1.00 for the Portfolio as computed for the purpose of sales and redemptions.
Such procedures include review of the Portfolio's portfolio holdings by the
Board of Trustees, at such intervals as they may deem appropriate, to determine
whether the net asset value calculated by using available market quotations or
other reputable sources for the Portfolio deviates from $1.00 per share and, if
so, whether such deviation may result in material dilution or is otherwise
unfair to existing holders of the Portfolio's shares. In the event the Board of
Trustees determines that such a deviation exists for the Portfolio, it will take
such corrective action as the Board of Trustees deems necessary and appropriate
with respect to the Portfolio, including the sale of portfolio instruments prior
to maturity to realize capital gains or losses or to shorten the average
portfolio maturity; the withholding of dividends; redemption of shares in kind;
or the establishment of a net asset value per share by using available market
quotations.


DISTRIBUTION AGREEMENT 

  The Fund has entered into a Master Distribution Agreement dated as of October
18, 1993 (the "Distribution Agreement") with FMC, a registered broker-dealer and
a wholly-owned subsidiary of AIM, to act as the exclusive distributor of the
shares of the Class. The address of FMC is 11 Greenway Plaza, Suite 1919,
Houston, Texas 77046-1173. See "General Information About the Fund -- Trustees
and Officers" and "-- Investment Advisor" for information as to the affiliation
of certain trustees and officers of the Fund with FMC, AIM and AIM Management.

  The Distribution Agreement provides that FMC has the exclusive right to
distribute shares of the Portfolio either directly or through other broker-
dealers. The Distribution Agreement also provides that FMC will pay promotional
expenses, including the incremental costs of printing prospectuses and
statements of additional information, annual reports and other periodic reports
for distribution to persons who are not shareholders of the Fund and the costs
of preparing and distributing any other supplemental sales literature. FMC has
not undertaken to sell any specified number of shares of the Class. FMC does not
receive any fees with respect to the shares of the Class pursuant to the
Distribution Agreement.
 
  On July 19, 1993, the Board of Trustees (including the affirmative vote of all
the trustees who are not parties to the Distribution Agreement or "interested
persons" of any such party) initially approved the Distribution Agreement for
its initial term. The Distribution Agreement will remain in effect until June
30, 1995, and it will continue in effect from year to year thereafter only if
such continuation is specifically approved at least annually by the Fund's Board
of Trustees and the affirmative vote of the trustees who are not parties to the
Distribution Agreement or "interested persons" of any such party by votes cast
in person at a meeting called for such purpose. A prior distribution agreement
between the Fund and FMC, with terms substantially the same as those of the
Distribution Agreement, was in effect through October 15, 1993. The Fund or FMC
may terminate the Distribution Agreement on sixty days' written notice without
penalty. The Distribution Agreement will terminate automatically in the event of
its "assignment," as defined in the 1940 Act.


PERFORMANCE INFORMATION 

  As stated under the caption "Yield Information" in the Prospectus, yield
information for the shares of the Class may be obtained by calling the Fund at
(800) 659-1005. The current yield quoted will be the net average annualized
yield for an identified period, usually seven consecutive calendar days. Current
yield will be computed by assuming that an account was established with a single
share (the "Single Share Account") on the first day of the period. To arrive at
the quoted yield, the net change in the value of that Single Share Account for
the period (which would include dividends accrued with respect to the share, and
dividends declared on shares purchased with dividends accrued and paid, if any,
but would not include realized gains and losses or unrealized appreciation or
depreciation) will be multiplied by 365 and then divided by the number of days
in the period, with the resulting figure carried to the nearest hundredth of one
percent. The Fund may also furnish a quotation of effective yield that assumes
the reinvestment of dividends for a 365-day year and a return for the entire
year equal to the average

                                     A-14
<PAGE>
 
annualized yield for the period, which will be computed by compounding the
unannualized current yield for the period by adding 1 to the unannualized
current yield, raising the sum to a power equal to 365 divided by the number of
days in the period, and then subtracting 1 from the result.

  For the seven-day period ended August 31, 1994, the current yield and the
effective yield (which assumes the reinvestment of dividends for a 365-day year
and a return for the entire year equal to the annualized current yield for the
period) for the Class were 4.10% and 4.18%, respectively. These yields are
quoted for illustration purposes only. The yields for any other seven-day period
may be substantially different from the yields quoted above.

  The Portfolio may compare the performance of the Class or the performance of
securities in which it may invest to:

  . IBC/Donoghue's Money Fund Averages, which are average yields of various
 types of money market funds that include the effect of compounding
 distributions;

  . other mutual funds, especially those with similar investment objectives.
 These comparisons may be based on data published by IBC/Donoghue's Money Fund
 Report of Holliston, MA 01746 or by Lipper Analytical Services, Inc., a widely
 recognized independent service located in Summit, New Jersey, which monitors
 the performance of mutual funds;

  . yields on other money market securities or averages of other money market
 securities as reported by the Federal Reserve Bulletin, by TeleRate, a
 financial information network, or by Bloomberg, a financial information firm;
 and

  . other fixed-income investments such as Certificates of Deposit (CDs).

  The principal value and interest rate of CDs and money market securities are
fixed at the time of purchase whereas the Class' yield will fluctuate. Unlike
some CDs and certain other money market securities, money market mutual funds
are not insured by the FDIC. Investors should give consideration to the quality
and maturity of the Portfolio's securities when comparing investment
alternatives.

  The Portfolio may reference the growth and variety of money market mutual
funds and AIM's innovation and participation in the industry.


SUSPENSION OF REDEMPTION RIGHTS 

  The right of redemption may be suspended or the date of payment upon
redemption may be postponed when (a) trading on the New York Stock Exchange is
restricted, as determined by applicable rules and regulations of the SEC, (b)
the New York Stock Exchange is closed for other than customary weekend or
holiday closings, (c) the SEC has by order permitted such suspension, or (d) an
emergency as determined by the SEC exists making disposition of portfolio
securities or the valuation of the net assets of the Portfolio not reasonably
practicable.


                      INVESTMENT PROGRAM AND RESTRICTIONS

INVESTMENT PROGRAM

  The Portfolio seeks to achieve its objective by investing in high grade money
market instruments. The money market instruments in which the Portfolio invests
are considered to carry very little risk and accordingly may not have as high a
yield as that available on money market instruments of lesser quality. The
Portfolio invests exclusively in direct obligations of the U.S. Treasury, which
include Treasury bills, notes and bonds.


ELIGIBLE SECURITIES

  The Portfolio limits its investments to direct U.S. Treasury obligations.
These securities are "Eligible Securities" as defined in Rule 2a-7. Rule 2a-7
limits securities that may be purchased by money market funds to "Eligible
Securities," and defines an "Eligible Security" as follows:

      (i) a security with a remaining maturity of 397 days or less that is rated
    (or that has been issued by an issuer that is rated with respect to a class
    of short-term debt obligations, or any security within that class, that is
    comparable in priority and security with the security) by the Requisite
    NRSROs(1) in one of the two highest rating categories
- ---------------
(1)  "Requisite NRSRO" shall mean (a) any two nationally recognized statistical 
     rating organizations that have issued a rating with respect to a security
     or class of debt obligations of an issuer, or (b) if only one NRSRO has
     issued a rating with respect to such security or issuer at security, that
     NRSRO. At present the NRSROs are: Standard & Poor's Corp., ("S&P"), Moody's
     Investors Service, Inc., ("Moody's"), Duff and Phelps, Inc., Fitch
     Investors Services, Inc. and, with respect to certain types of securities,
     IBCA Limited and its affiliate, IBCA Inc. Subcategories or gradations in
     ratings (such as a "+" or "-") do not count as rating categories. 

                                     A-15
<PAGE>
 
   for short-term debt obligations (within which there may be sub-categories or
   gradations indicating relative standing); or

     (ii) a security:

       (A) that at the time of issuance was a long-term security but that has a
     remaining maturity of 397 calendar days or less, and

       (B) whose issuer has received from the Requisite NRSROs a rating, with
     respect to a class of short-term debt obligations (or any security within
     that class) that is now comparable in priority and security with the
     security, in one of the two highest rating categories for short-term debt
     obligations (within which there may be sub-categories or gradations
     indicating relative standing); or

     (iii) an Unrated Security(2) that is of comparable quality to a security
   meeting the requirements of paragraphs (a)(5)(i) or (ii) of this section, as
   determined by the money market fund's board of trustees; provided, however,
   that:

       (A) the board of trustees may base its determination that a Standby
     Commitment is an Eligible Security upon a finding that the issuer of the
     commitment presents a minimal risk of default; and

       (B) a security that at the time of issuance was a long-term security but
     that has a remaining maturity of 397 calendar days or less and that is an
     unrated security is not an Eligible Security if the security has a long-
     term rating from any NRSRO that is not within the NRSRO's two highest
     categories (within which there may be sub-categories or gradations
     indicating relative standing).

  The securities purchased by the Portfolio, which are limited to those issued
by the U.S. Treasury, are considered to be in the highest ratings category for
short-term debt obligations.


INVESTMENT RESTRICTIONS 

  As a matter of fundamental policy which may not be changed without a majority
vote of shareholders of the Portfolio (as that term is defined under "General
Information about the Fund -- The Fund and its Shares"), the Portfolio may not:

    (1) borrow money or issue senior securities except (a) for temporary or
  emergency purposes (e.g., in order to facilitate the orderly sale of portfolio
  securities or to accommodate abnormally heavy redemption requests), the
  Portfolio may borrow money from banks or obtain funds by entering into reverse
  repurchase agreements, and (b) to the extent that entering into commitments to
  purchase securities in accordance with the Portfolio's investment program may
  be considered the issuance of senior securities, provided that the Portfolio
  will not purchase portfolio securities while borrowings in excess of 5% of its
  total assets are outstanding;

    (2) mortgage, pledge or hypothecate any assets except to secure permitted
  borrowings and except for reverse repurchase agreements and then only in an
  amount up to 33 1/3% of the value of its total assets at the time of borrowing
  or entering into a reverse repurchase agreement;

    (3) make loans of money or securities other than (a) through the purchase of
  debt securities in accordance with the Portfolio's investment program, (b) by
  entering into repurchase agreements and (c) by lending portfolio securities to
  the extent permitted by law or regulation;

    (4) underwrite securities issued by any other person, except to the extent
  that the purchase of securities and the later disposition of such securities
  in accordance with the Portfolio's investment program may be deemed an
  underwriting;

    (5) invest in real estate, except that the Portfolio may purchase and sell
  securities secured by real estate or interests therein or issued by issuers
  which invest in real estate or interests therein;

    (6) purchase or sell commodities or commodity futures contracts, purchase
  securities on margin, make short sales or invest in puts or calls;
- ---------------
(2)  An "unrated security" is a security (i) issued by an issuer that does not
     have a current short-term rating from any NRSRO, either as to the
     particular security or as to any other short-term obligations of comparable
     priority and security; (ii) that was a long-term security at the time of
     issuance and whose issuer has not received from any NRSRO a rating with
     respect to a class of short-term debt obligations now comparable in
     priority and security; or (iii) a security that is rated but which is the
     subject of an external credit support agreement not in effect when the
     security was assigned its rating, provided that a security is not an
     unrated security if any short-term debt obligation issued by the issuer and
     comparable in priority and security is rated by any NRSRO.

                                     A-16
<PAGE>
 
    (7) invest in any obligation not payable as to principal and interest in 
  United States currency; or

    (8) acquire for value the securities of any other investment company, except
  in connection with a merger, consolidation, reorganization or acquisition of
  assets.


OTHER INVESTMENT POLICIES

  The Portfolio does not intend to invest in companies for the purpose of
exercising control or management. The Portfolio may also lend its portfolio
securities in amounts up to 33 1/3% of its total assets to financial
institutions in accordance with the investment restrictions of the Portfolio.
Such loans would involve risks of delay in receiving additional collateral in
the event the value of the collateral decreased below the value of the
securities loaned, or of delay in recovering the securities loaned, or even loss
of rights in the collateral should the borrower of the securities fail
financially. However, loans will be made only to borrowers deemed by AIM to be
of good standing and only when, in AIM's judgment, the income to be earned from
the loans justifies the attendant risks. None of the foregoing policies is
fundamental.

  The Fund may, from time to time in order to qualify shares of the Portfolio
for sale in a particular state, agree to certain investment restrictions in
addition to or more stringent than those set forth above. Such restrictions are
not fundamental and may be changed without the approval of shareholders. For
example, the Portfolio will not invest in oil, gas or other mineral leases,
rights, royalty contracts or exploration or development programs (Texas). This
restriction, however, does not prevent the Portfolio from purchasing and selling
securities of companies engaged in the exploration, development, production,
refining, transporting and marketing of oil, gas or minerals.

 
                            PORTFOLIO TRANSACTIONS

  AIM is responsible for decisions to buy and sell securities for the Portfolio,
broker-dealer selection and negotiation of commission rates. Since purchases and
sales of portfolio securities by the Portfolio are usually principal
transactions, the Portfolio incurs little or no brokerage commissions. Portfolio
securities are normally purchased directly from the issuer or from a market
maker for the securities. The purchase price paid to dealers serving as market
makers may include a spread between the bid and asked prices.

  The Portfolio does not seek to profit from short-term trading, and will
generally (but not always) hold portfolio securities to maturity, but AIM may
seek to enhance the yield of the Portfolio by taking advantage of yield
disparities or other factors that occur in the money markets. For example,
market conditions frequently result in similar securities trading at different
prices. AIM may dispose of any portfolio security prior to its maturity if such
disposition and reinvestment of proceeds are expected to enhance yield
consistent with AIM's judgment as to desirable portfolio maturity structure or
if such disposition is believed to be advisable due to other circumstances or
conditions. The amortized cost method of valuing portfolio securities requires
that the Portfolio maintain an average weighted portfolio maturity of ninety
days or less. Thus, there is likely to be relatively high portfolio turnover,
but since brokerage commissions are not normally paid on money market
instruments, the high rate of portfolio turnover is not expected to have a
material effect on the net income or expenses of the Portfolio.

  AIM's primary consideration in effecting a security transaction is to obtain
the best net price and the most favorable execution of the order. To the extent
that the execution and prices offered by more than one dealer are comparable,
AIM may, in its discretion, effect transactions with dealers that furnish
statistical, research or other information or services which are deemed by AIM
to be beneficial to the Portfolio's investment program. Certain research
services furnished by dealers may be useful to AIM with respect to clients other
than the Portfolio. Similarly, any research services received by AIM through
placement of portfolio transactions of other clients may be of value to AIM in
fulfilling its obligations to the Portfolio. AIM is of the opinion that the
material received is beneficial in supplementing AIM's research and analysis,
and, therefore, it may benefit the Portfolio by improving the quality of AIM's
investment advice. The advisory fees paid by the Portfolio are not reduced
because AIM receives such services.

  Provisions of the 1940 Act and rules and regulations thereunder have been
construed to prohibit the Fund from purchasing securities or instruments from,
or selling securities or instruments to, any holder of 5% or more of the voting
securities of any investment company managed or advised by AIM. The Fund has
obtained an order of exemption from the SEC which permits the Fund to engage in
certain transactions with such 5% holder, if the Fund complies with conditions
and procedures designed to ensure that such transactions are executed at fair
market value and present no conflicts of interest.

  AIM and its affiliates manage several other investment accounts, some of which
may have objectives similar to the Portfolio's. It is possible that at times
identical securities will be acceptable for one or more of such investment
accounts. However, the position of each account in the securities of the same
issue may vary and the length of time that each account may choose to hold its
investment in the securities of the same issue may likewise vary. The timing and
amount of purchase by each account

                                     A-17
<PAGE>
 
will also be determined by its cash position. If the purchase or sale of
securities is consistent with the investment policies of the Portfolio and one
or more of these accounts and is considered at or about the same time,
transactions in such securities will be allocated in good faith among such
accounts, in accordance with applicable laws and regulations, in order to obtain
the best net price and most favorable execution. The allocation and combination
of simultaneous securities purchases on behalf of the Portfolio will be made in
the same way that such purchases are allocated among or combined with those of
other AIM accounts. Simultaneous transactions could adversely affect the ability
of the Portfolio to obtain or dispose of the full amount of a security which it
seeks to purchase or sell.

  Under the 1940 Act, persons affiliated with the Fund are prohibited from
dealing with the Portfolios as principal in any purchase or sale of securities
unless an exemptive order allowing such transactions is obtained from the SEC.
The Board of Trustees has adopted procedures pursuant to Rule 17a-7 under the
1940 Act relating to portfolio transactions among the Portfolios and the AIM
Funds and each of the Portfolios may from time to time enter into transactions
in accordance with such Rule and procedures.


                                  TAX MATTERS

  The following is only a summary of certain additional tax considerations
generally affecting the Portfolio and its shareholders that are not described in
the Prospectus. No attempt is made to present a detailed explanation of the tax
treatment of the Portfolio or its shareholders, and the discussion here and in
the Prospectus is not intended as a substitute for careful tax planning.


QUALIFICATION AS A REGULATED INVESTMENT COMPANY 

  The Portfolio has elected to be taxed as a regulated investment company under
Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). As a
regulated investment company, the Portfolio is not subject to federal income tax
on the portion of its net investment income (i.e., taxable interest, dividends
and other taxable ordinary income, net of expenses) and capital gain net income
(i.e., the excess of capital gains over capital losses) that it distributes to
shareholders, provided that it distributes at least 90% of its investment
company taxable income (i.e., net investment income and the excess of net short-
term capital gain over net long-term capital loss) for the taxable year (the
"Distribution Requirement"), and satisfies certain other requirements of the
Code that are described below. Distributions by the Portfolio made during the
taxable year or, under specified circumstances, within twelve months after the
close of the taxable year, will be considered distributions of income and gains
for the taxable year and can therefore satisfy the Distribution Requirement.

  In addition to satisfying the Distribution Requirement, a regulated investment
company must (1) derive at least 90% of its gross income from dividends,
interest, certain payments with respect to securities loans, gains from the sale
or other disposition of stock or securities or foreign currencies (to the extent
such currency gains are directly related to the regulated investment company's
principal business of investing in stock or securities) and other income
(including but not limited to gains from options, futures or forward contracts)
derived with respect to its business of investing in such stock, securities or
currencies (the "Income Requirement"); and (2) derive less than 30% of its gross
income (exclusive of certain gains on designated hedging transactions that are
offset by realized or unrealized losses on offsetting positions) from the sale
or other disposition of stock, securities or foreign currencies (or options,
futures or forward contracts thereon) held for less than three months (the
"Short-Short Gain Test"). However, foreign currency gains, including those
derived from options, futures and forward contracts, will not be characterized
as Short-Short Gain if they are directly related to the regulated investment
company's principal business of investing in stock or securities (or options or
futures thereon). Because of the Short-Short Gain Test, the Portfolio may have
to limit the sale of appreciated securities that it has held for less than three
months. However, the Short-Short Gain Test will not prevent the Portfolio from
disposing of investments at a loss, since the recognition of a loss before the
expiration of the three-month holding period is disregarded. Interest (including
original issue discount) received by the Portfolio at maturity or upon the
disposition of a security held for less than three months will not be treated as
gross income derived from the sale or other disposition of a security within the
meaning of the Short-Short Gain Test. However, income that is attributable to
realized market appreciation will be treated as gross income from the sale or
other disposition of securities for this purpose.

  In addition to satisfying the requirements described above, the Portfolio must
satisfy an asset diversification test in order to qualify for tax purposes as a
regulated investment company. Under this test, at the close of each quarter of
the Portfolio's taxable year, at least 50% of the value of the Portfolio's
assets must consist of cash and cash items, U.S. Government securities,
securities of other regulated investment companies, and securities of other
issuers (as to which the Portfolio has not invested more than 5% of the value of
the Portfolio's total assets in securities of such issuer and as to which the
Portfolio does not hold more than 10% of the outstanding voting securities of
such issuer), and no more than 25% of the value of its total assets may be
invested in the securities of any other issuer (other than U.S. Government
securities and securities of other regulated invest

                                     A-18
<PAGE>
 
ment companies), or in two or more issuers which the Portfolio controls and
which are engaged in the same or similar trades or businesses.

  If for any taxable year the Portfolio does not qualify as a regulated
investment company, all of its taxable income (including its net capital gain)
will be subject to tax at regular corporate rates without any deduction for
distributions to shareholders, and such distributions will be taxable as
ordinary dividends to the extent of the Portfolio's current and accumulated
earnings and profits. Such distributions generally will be eligible for the
dividends received deduction in the case of corporate shareholders.

EXCISE TAX ON REGULATED INVESTMENT COMPANIES 

  A 4% non-deductible excise tax is imposed on a regulated investment company
that fails to distribute in each calendar year an amount equal to 98% of
ordinary taxable income for the calendar year and 98% of capital gain net income
for the one-year period ended on October 31 of such calendar year (or, at the
election of a regulated investment company having a taxable year ending November
30 or December 31, for its taxable year (a "taxable year election")). The
balance of such income must be distributed during the next calendar year. For
the foregoing purposes, a regulated investment company is treated as having
distributed any amount on which it is subject to income tax for any taxable year
ending in such calendar year.

  For purposes of the excise tax, a regulated investment company (1) may reduce
its capital gain net income (but not below its net capital gain) by the amount
of any net ordinary loss for the calendar year and (2) must, unless it has made
a taxable year election, exclude foreign currency gains and losses incurred
after October 31 of any year in determining the amount of ordinary taxable
income for the current calendar year (and, instead, include such gains and
losses in determining ordinary taxable income for the succeeding calendar year).

  The Portfolio intends to make sufficient distributions or deemed distributions
of its ordinary taxable income and capital gain net income prior to the end of
each calendar year to avoid liability for the excise tax. However, investors
should note that the Portfolio may in certain circumstances be required to
liquidate portfolio investments to make sufficient distributions to avoid excise
tax liability.


PORTFOLIO DISTRIBUTIONS 

  The Portfolio anticipates distributing substantially all of its investment
company taxable income for each taxable year. Such distributions will be taxable
to shareholders as ordinary income and treated as dividends for federal income
tax purposes, but they will not qualify for the 70% dividends received deduction
for corporations.

  The Portfolio may either retain or distribute to shareholders its net capital
gain for each taxable year. The Portfolio currently intends to distribute any
such amounts. If net capital gain is distributed and designated as a capital
gain dividend, it will be taxable to shareholders as long-term capital gain,
regardless of the length of time the shareholder has held his shares or whether
such gain was recognized by the Portfolio prior to the date on which the
shareholder acquired his shares. Conversely, if the Portfolio elects to retain
its net capital gain, the Portfolio will be taxed thereon (except to the extent
of any available capital loss carryovers) at the current corporate tax rate. If
the Portfolio elects to retain net capital gain, it is expected that the
Portfolio also will elect to have shareholders treated as having received a
distribution of such gain, with the results that they will be required to report
their respective shares of such gain on their tax returns as long-term capital
gain, will receive a refundable tax credit for their allocable share of tax paid
by the Portfolio on the gain, and will increase the tax basis for their shares
by an amount equal to the deemed distribution less the tax credit.

  Distributions by the Portfolio that do not constitute ordinary income
dividends or capital gain dividends will be treated as a return of capital to
the extent of (and in reduction of) the shareholder's tax basis in his shares;
any excess will be treated as gain from the sale of his shares, as discussed
below.

  Distributions by the Portfolio will be treated in the manner described above
regardless of whether such distributions are paid in cash or reinvested in
additional shares of the Class. Shareholders receiving a distribution in the
form of additional shares will be treated as receiving a distribution in an
amount equal to the fair market value of the shares received, determined as of
the reinvestment date. In addition, if the net asset value at the time a
shareholder purchases shares of the Class reflects undistributed net investment
income or recognized capital gain net income, or unrealized appreciation in the
value of the assets of the Portfolio, distributions of such amounts will be
taxable to the shareholder in the manner described above, although such
distributions economically constitute a return of capital to the shareholder.

  Ordinarily, shareholders are required to take distributions by the Portfolio
into account in the year in which the distributions are made. However,
distributions declared in October, November or December of any year and payable
to shareholders of record on a specified date in such a month will be deemed to
have been received by the shareholders (and made by the Portfolio)

                                     A-19
<PAGE>
 
on December 31 of such calendar year if such distributions are actually made in
January of the following year. Shareholders will be advised annually as to the
U.S. federal income tax consequences of distributions made (or deemed made)
during the year.

  The Portfolio will be required in certain cases to withhold and remit to the
U.S. Treasury 31% of ordinary income dividends and capital gain dividends, and
the proceeds of redemption of shares, paid to any shareholder (1) who has
provided either an incorrect tax identification number or no number at all, (2)
who is subject to backup withholding by the Internal Revenue Service for failure
to report the receipt of interest or dividend income properly, or (3) who has
failed to certify to the Portfolio that it is not subject to backup withholding
or that it is a corporation or other "exempt recipient."


SALE OR REDEMPTION OF SHARES 

  A shareholder will recognize gain or loss on the sale or redemption of shares
of the Class in an amount equal to the difference between the proceeds of the
sale or redemption and the shareholder's adjusted tax basis in the shares. All
or a portion of any loss so recognized may be disallowed if the shareholder
purchases other shares of the Class within 30 days before or after the sale or
redemption. In general, any gain or loss arising from (or treated as arising
from) the sale or redemption of shares of the Class will be considered capital
gain or loss and will be long-term capital gain or loss if the shares were held
for longer than one year. However, any capital loss arising from the sale or
redemption of shares held for six months or less will be treated as a long-term
capital loss to the extent of the amount of capital gain dividends received on
such shares. For this purpose, the special holding period rules of Code Section
246(c)(3) and (4) generally will apply in determining the holding period of
shares.


FOREIGN SHAREHOLDERS 

  Taxation of a shareholder who, as to the United States, is a nonresident alien
individual, foreign trust or estate, foreign corporation, or foreign partnership
("foreign shareholder"), depends on whether the income from the Portfolio is
"effectively connected" with a U.S. trade or business carried on by such
shareholder.

  If the income from the Portfolio is not effectively connected with a U.S.
trade or business carried on by a foreign shareholder, dividends and
distributions (other than capital gains dividends) will be subject to U.S.
withholding tax at the rate of 30% (or lower treaty rate) upon the gross amount
of the dividend or distribution. Such a foreign shareholder would generally be
exempt from U.S. federal income tax on gains realized on the sale of shares of
the Class, capital gain dividends and amounts retained by the Portfolio that are
designated as undistributed capital gains.

  If the income from the Portfolio is effectively connected with a U.S. trade or
business carried on by a foreign shareholder, then ordinary income dividends,
capital gain dividends and any gains realized upon the sale of shares of the
Portfolio will be subject to U.S. federal income tax at the rates applicable to
U.S. citizens or domestic corporations.

  In the case of foreign noncorporate shareholders, the Portfolio may be
required to withhold U.S. federal income tax at a rate of 31% on distributions
that are otherwise exempt from withholding tax unless such shareholders furnish
the Portfolio with proper notification of their foreign status.

  The tax consequences to a foreign shareholder entitled to claim the benefits
of an applicable tax treaty may be different from those described herein.
Foreign shareholders are urged to consult their own tax advisers with respect to
the particular tax consequences to them of an investment in the Portfolio,
including the applicability of foreign taxes.


EFFECT OF FUTURE LEGISLATION; STATE AND LOCAL TAX CONSIDERATIONS 

  The foregoing general discussion of U.S. federal income tax consequences is
based on the Code and the regulations issued thereunder as in effect on the date
of this Statement of Additional Information. Future legislative or
administrative changes or court decisions may significantly change the
conclusions expressed herein, and any such changes or decisions may have a
retroactive effect with respect to the transactions contemplated herein.

  Rules of state and local taxation of ordinary income dividends and capital
gain dividends from regulated investment companies often differ from the rules
for U.S. federal income taxation described above. It is anticipated that the
ordinary income dividends paid by the Portfolio from net investment income will
be exempt from state and local personal and, in some cases, corporate income
taxes in many states. Shareholders are urged to consult their tax advisers as to
the consequences of these and other state and local tax rules affecting their
investment in the Portfolio.

                                     A-20
<PAGE>

INDEPENDENT        To the Shareholders and Board of Trustees
AUDITORS' REPORT   Short-Term Investments Trust

                     We have audited the accompanying statement of assets and
                   liabilities of Treasury Tax-Advantage Portfolio, (a series
                   portfolio of Short-Term Investments Trust), including the
                   schedule of investments, as of August 31, 1994, and the
                   related statement of operations for the year then ended, the
                   statement of changes in net assets for each of the years in
                   the two-year period then ended, and the financial highlights
                   for each of the years in the four-year period then ended and
                   the period August 17, 1990 (date operations commenced)
                   through August 31, 1990. These financial statements and
                   financial highlights are the responsibility of the Fund's
                   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 securities owned as of
                   August 31, 1994, by correspondence with the custodian. 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 the Treasury TaxAdvantage
                   Portfolio as of August 31, 1994, the results of its
                   operations for the year then ended, the changes in its net
                   assets for each of the years in the two-year period then
                   ended, and the financial highlights for each of the years in
                   the four-year period then ended and the period August 17,
                   1990 (date operations commenced) through August 31, 1990, in
                   conformity with generally accepted accounting principles.

 

                                        KPMG Peat Marwick LLP

                   Houston, Texas
                   October 7, 1994

                                     FS-1
<PAGE>

                           <TABLE> 
                           <CAPTION>
                                                                     MATURITY  PAR(000)     VALUE           
                                                                     --------------------------------       
                           <S>                                       <C>       <C>       <C>                
SCHEDULE OF                U.S. TREASURY SECURITIES                                                         
INVESTMENTS                U.S. TREASURY BILLS(a)                                                           
August 31, 1994              4.02%.................................  09/01/94  $ 22,345  $ 22,345,000       
                             4.04%.................................  09/01/94    17,680    17,680,000       
                             4.00%.................................  09/08/94    15,000    14,988,334       
                             4.035%................................  09/08/94    25,000    24,980,385       
                             4.085%................................  09/08/94       175       174,861       
                             4.11%.................................  09/15/94    20,000    19,968,033       
                             4.15%.................................  09/15/94       670       668,919       
                             4.11%.................................  09/22/94     9,565     9,542,068       
                             4.17%.................................  09/22/94     9,140     9,117,767       
                             4.18%.................................  09/22/94    30,050    29,976,728       
                             4.29%.................................  09/22/94     2,425     2,418,931       
                             4.36%.................................  09/22/94    16,905    16,862,005       
                             4.37%.................................  09/22/94     6,975     6,957,219       
                             4.38%.................................  09/22/94     5,000     4,987,225       
                             4.22%.................................  10/06/94    14,270    14,211,453       
                             4.25%.................................  10/06/94       500       497,934       
                             4.275%................................  10/06/94    10,960    10,914,448       
                             4.355%................................  10/13/94    20,000    19,898,383       
                             4.30%.................................  10/20/94    17,385    17,283,249       
                             4.365%................................  10/20/94     7,895     7,848,094       
                             4.39%.................................  10/20/94    25,000    24,850,618       
                             4.41%.................................  10/20/94     7,100     7,057,382       
                             4.43%.................................  10/20/94     3,240     3,220,464       
                                                                                                            
                           U.S. TREASURY NOTES                                                              
                             4.00%.................................  09/30/94    23,750    23,743,497       
                             8.50%.................................  09/30/94    54,535    54,707,161       
                             9.50%.................................  10/15/94     7,925     7,971,792       
                             4.25%.................................  10/31/94     7,550     7,544,382       
                             6.00%.................................  11/15/94    21,750    21,803,660       
                                                                                         ------------       
                           Total U.S. Treasury Securities..............................   402,219,992       
                                                                                         ------------       
                           TOTAL INVESTMENTS -- 99.59%(b)..............................  $402,219,992(c)    
                                                                                         ============       
                           (a) U.S. Treasury bills are traded on a discount basis. In such cases the        
                               interest rate shown represents the rate of discount paid or received at      
                               the time of purchase by the Fund.                                            
                                                                                                            
                           (b) Percentage of Net Assets.                                                    
                                                                                                            
                           (c) Also represents cost for federal income tax purposes.                        
                                                                                                            
                           See Notes to Financial Statements 
                           </TABLE>

                                     FS-2
<PAGE>

                           <TABLE>
                           <S>                                                               <C>             
STATEMENT OF ASSETS        ASSETS:                                                                           
AND LIABILITIES            Investments at value (amortized cost)...........................  $402,219,992    
August 31, 1994            Cash............................................................           689    
                           Interest receivable.............................................     3,128,532    
                           Investment for deferred compensation plan.......................         2,272    
                           Other assets....................................................        37,526    
                                                                                             ------------    
                             Total assets..................................................   405,389,011    
                                                                                             ------------    
                           LIABILITIES:                                                                      
                           Dividends payable...............................................     1,413,482    
                           Deferred compensation payable...................................         2,272    
                           Accrued advisory fees...........................................        63,792    
                           Accrued trustees' fees..........................................         1,166    
                           Accrued administrative service fees.............................         5,773    
                           Accrued operating expenses......................................        20,821    
                                                                                             ------------    
                             Total liabilities.............................................     1,507,306    
                                                                                             ------------    
                           NET ASSETS......................................................  $403,881,705    
                                                                                             ============    
                           NET ASSET VALUE PER SHARE:                                                        
                           Shares outstanding, $.01 par value per share....................   403,826,236    
                                                                                             ============    
                           Net asset value, offering and redemption price per share........         $1.00    
                                                                                                    =====    
                                                                                                             
                           See Notes to Financial Statements.                                                
                           </TABLE>
                                                                           
                                     FS-3
<PAGE>

                           <TABLE>
                           <S>                                                                  <C>
STATEMENT OF               INVESTMENT INCOME:                                                                   
OPERATIONS                 Interest income....................................................  $14,788,923     
For the                                                                                         -----------     
year ended                 EXPENSES:                                                                            
August 31, 1994            Advisory fees......................................................      640,698     
                           Custodian fees.....................................................       34,928     
                           Administrative service fees........................................       31,534     
                           Trustees' fees and expenses........................................        8,407     
                           Transfer agent fees................................................        9,933     
                           Professional fees..................................................       40,999     
                           Printing expenses..................................................       40,165     
                           Other..............................................................       55,682     
                                                                                                -----------     
                             Total expenses...................................................      862,346     
                                                                                                -----------     
                           Net investment income..............................................   13,926,577     
                           Net realized gain on sales of investments..........................       12,246     
                                                                                                -----------     
                           Net increase in net assets resulting from operations...............  $13,938,823     
                                                                                                ===========     
                                                                                                                
                           See Notes to Financial Statements.
                           </TABLE>

                                     FS-4
<PAGE>

                           <TABLE>
                           <CAPTION>
                                                                                   1994          1993          
                                                                               ------------  -------------     
                           <S>                                                 <C>           <C>               
STATEMENT                  OPERATIONS:                                                                         
OF CHANGES IN               Net investment income............................. $ 13,926,577  $  15,489,179     
NET ASSETS                  Net realized gain (loss) on sales of investments..       12,246         (1,376)    
For the years                                                                  ------------  -------------     
ended August 31,             Net increase in net assets resulting from                                         
1994 and 1993                 operations......................................   13,938,823     15,487,803     
                           Distributions to shareholders from net investment                                   
                            income............................................  (13,926,577)   (15,489,179)    
                           Share transactions -- net..........................  (30,823,909)  (138,587,971)    
                                                                               ------------  -------------     
                             Net increase (decrease) in net assets............  (30,811,663)  (138,589,347)    
                           NET ASSETS:                                                                         
                            Beginning of period...............................  434,693,368    573,282,715     
                                                                               ------------  -------------     
                            End of period..................................... $403,881,705  $ 434,693,368     
                                                                               ============  =============     
                           NET ASSETS CONSIST OF:                                                              
                            Shares of beneficial interest..................... $403,826,236  $ 434,650,145     
                            Undistributed net realized gain on sales of                                        
                             investments......................................       55,469         43,223     
                                                                               ------------  -------------     
                                                                               $403,881,705  $ 434,693,368     
                                                                               ============  =============     
                                                                                                               
                            See Notes to Financial Statements.
                            </TABLE> 

                                     FS-5
<PAGE>

NOTES TO                   NOTE 1 - SIGNIFICANT ACCOUNTING POLICIES
FINANCIAL                                                          
STATEMENTS                   Short-Term Investments Trust (the "Fund") is
August 31, 1994            registered under the Investment Company Act of 1940,
                           as amended, as an open-end series, diversified
                           management investment company. The Fund is organized
                           as a Delaware business trust consisting of two
                           different portfolios, each of which offers separate
                           series of shares: the Treasury Portfolio and the
                           Treasury TaxAdvantage Portfolio with the assets,
                           liabilities and operations of each portfolio
                           accounted for separately. Information presented in
                           these financial statements pertains only to the
                           Treasury TaxAdvantage Portfolio (the "Portfolio").

                             The following is a summary of the significant
                           accounting policies followed by the Portfolio in the
                           preparation of its financial statements.

                           A. Security Valuations - The Portfolio invests only
                              in securities which have maturities of 397 days or
                              less. The securities are valued on the basis of
                              amortized cost which approximates market value.
                              This method values a security at its cost on the
                              date of purchase and thereafter assumes a constant
                              amortization to maturity of any discount or
                              premium.

                           B. Securities Transactions, Investment Income and
                              Distributions - Securities transactions are
                              accounted for on a trade date basis. Realized
                              gains or losses are computed on the basis of
                              specific identification of the securities sold.
                              Interest income, adjusted for amortization of
                              premiums and discounts on investments, is accrued
                              daily. Dividends to shareholders are declared
                              daily and are paid on the first business day of
                              the following month.

                           C. Federal Income Taxes - The Portfolio intends to
                              comply with the requirements of the Internal
                              Revenue Code necessary to qualify as a regulated
                              investment company and, as such, will not be
                              subject to federal income taxes on otherwise
                              taxable income (including net realized capital
                              gains) which is distributed to shareholders.
                              Therefore, no provision for federal income taxes
                              is recorded in the financial statements.

                           D. Expenses - Expenses of the Fund which are not
                              directly attributable to a specific portfolio or
                              class are prorated among the portfolios to which
                              the expense relates based on the relative net
                              assets of each portfolio.

                                     FS-6
<PAGE>
  
                         NOTE 2 - ADVISORY FEES AND OTHER TRANSACTIONS
                                  WITH AFFILIATES 

                           The Fund has entered into a master investment
                         advisory agreement with A I M Advisors, Inc. ("AIM").
                         Under the terms of the master advisory agreement, AIM
                         receives a monthly fee with respect to the Portfolio
                         calculated by applying a monthly rate, based upon the
                         following annual rates, to the average daily net assets
                         of the Portfolio:

                         Net Assets                                       Rate  
                         -----------------------------------------------  ----
                         First $250 million.............................   .20%
                         Over $250 million to $500 million..............   .15
                         Over $500 million..............................   .10 

                           AIM will, if necessary, reduce its fee for any fiscal
                         year to the extent required so that the amount of
                         ordinary expenses of the Portfolio (excluding interest,
                         taxes, brokerage commissions and extraordinary
                         expenses) paid or incurred by the Portfolio for such
                         fiscal year does not exceed the applicable expense
                         limitations imposed by the state securities regulations
                         in any state in which the Portfolio's shares are
                         qualified for sale. During the year ended August 31,
                         1994, AIM voluntarily waived advisory fees of $131,042.

                           The Portfolio, pursuant to its administrative
                         services agreement with AIM, has agreed to reimburse
                         AIM for certain costs incurred in providing
                         administrative services to the Portfolio. During the
                         year ended August 31, 1994 the Portfolio reimbursed AIM
                         $31,534 for such services.

                           Certain officers and trustees of the Fund are
                         officers and directors of AIM and Fund Management
                         Company, the Portfolio's distributor.

                           The Fund paid legal fees of $6,735 for services
                         rendered by Reid & Priest as counsel to the Board of
                         Trustees. In September 1994, Kramer, Levin, Naftalis,
                         Kamin & Frankel was appointed as counsel to the Board
                         of Trustees. A member of that firm is a trustee of the
                         Trust.


                         NOTE 3 - TRUSTEES' FEES 

                           Trustees' fees represent remuneration paid or accrued
                         to each trustee who is not an "interested person" of
                         the Fund. The Fund may invest trustees' fees, if so
                         elected by a trustee, in mutual fund shares in
                         accordance with a deferred compensation plan.

                                     FS-7
<PAGE>
 
NOTE 4 -- SHARE INFORMATION
 
  Changes in shares outstanding for the years ended August 31, 1994 and 1993
were as follows:

<TABLE> 
<CAPTION> 
                                1994                          1993  
                   ------------------------------   -------------------------------
<S>                <C>             <C>               <C>             <C> 
Sold.............  1,529,572,244   $1,529,572,244    1,475,242,445   $1,475,242,445
Issued as
 reinvestment of
 dividends.......         72,270           72,270              593              593
Reacquired....... (1,560,468,423)  (1,560,468,423)  (1,613,831,009)  (1,613,831,009)
                  --------------   --------------   --------------   --------------
Net increase
 (decrease)......    (30,823,909)    $(30,823,909)    (138,587,971)   $(138,587,971)
                  ==============   ==============   ==============   ==============
 
</TABLE> 
 

NOTE 5 -- FINANCIAL HIGHLIGHTS

  Shown below are the condensed financial highlights for a share outstanding
during each of the years in the four-year period ended August 31, 1994 and the
period August 17, 1990 (date operations commenced) through August 31, 1990.

<TABLE> 
<CAPTION> 
 
 

                                               August 31,   
                        ----------------------------------------------------------------
                          1994          1993        1992          1991            1990  
                        -------       --------    -------       --------        --------
<S>                     <C>           <C>         <C>           <C>             <C>  
Net asset value,
 beginning of
 period.............     $1.00          $1.00        $1.00         $1.00           $1.00
Income from
 investment
 operations:
Net investment
 income.............    0.0324         0.0293       0.0424        0.0650          0.0032
                       -------        -------      -------       -------         -------
Less distributions:
 Dividends from net
  investment
  income............   (0.0324)       (0.0293)     (0.0424)      (0.0650)        (0.0032)
                       -------        -------      -------       -------         -------
 
Net asset value,
 end of period......     $1.00          $1.00        $1.00         $1.00           $1.00
                       =======        =======      =======       =======         =======
Total return........      3.29 %         2.96 %       4.32 %        6.70 %          7.79 %(e) 
                       =======        =======      =======       =======         =======
 
Ratios/supplemental
 data:
Net assets, end of
 period (000s
 omitted)...........  $403,882        $434,693     $573,283       $403,846        $16,201
                      ========        ========     ========       ========        =======
 
Ratio of expenses
 to average net
 assets.............      0.20 %(a,b)     0.20 %       0.17 %(c)      0.14 %(c)      0.10 % (d,e)
                      ========        ========     ========       ========        =======
 
Ratio of net
 investment income
 to average net
 assets.............      3.23 %(a,b)     2.93 %       4.16 %(c)      6.16 %(c)      7.74 %(d,e) 
                      ========        ========     ========       ========        =======
 
</TABLE> 
- -------- 
(a) Based on average net assets of $431,159,563.

(b) After waiver of advisory fees. Ratio of expenses and net investment income
    to average net assets prior to waiver of advisory fees were 0.23% and 3.20%
    respectively.

(c) After waiver of advisory fees.

(d) After waiver of advisory fees and expense reimbursements.

(e) Annualized.

                                     FS-8
<PAGE>

=======================================  ====================================
                                                                              
SHORT-TERM INVESTMENTS TRUST                          PROSPECTUS 
11 Greenway Plaza, Suite 1919                                                 
Houston, Texas 77046-1173                          DECEMBER 21, 1994 
(713) 626-1005                                                              
                                                      SHORT-TERM  
INVESTMENT ADVISOR                                 INVESTMENTS TRUST
A I M ADVISORS, INC.                                                          
11 Greenway Plaza, Suite 1919                          --------- 
Houston, Texas 77046-1173                                                     
(713) 626-1919                                   TREASURY TAXADVANTAGE
                                                       PORTFOLIO 
DISTRIBUTOR                                                                   
FUND MANAGEMENT COMPANY                                ---------
11 Greenway Plaza, Suite 1919                                                  
Houston, Texas 77046-1173                         INSTITUTIONAL CLASS
(800) 659-1005                           
                                                                               
AUDITORS                                            TABLE OF CONTENTS
KPMG PEAT MARWICK LLP                                                           
NationsBank Building                     <TABLE>  
700 Louisiana Building                   <CAPTION>
Houston, Texas 77002                                                     Page  
                                                                         ----   
CUSTODIAN                                <S>                             <C>
THE BANK OF NEW YORK                     SUMMARY.....................       2   
110 Washington Street                                                           
8th Floor                                TABLE OF FEES AND EXPENSES..       4   
New York, New York 10286                                                      
                                         FINANCIAL HIGHLIGHTS........       5 
TRANSFER AGENTS                                                              
STATE STREET BANK AND TRUST COMPANY      SUITABILITY FOR INVESTORS...       6 
225 Franklin Street                                                          
Boston, Massachusetts 02110              INVESTMENT PROGRAM..........       6 
                                                                             
A I M INSTITUTIONAL FUND SERVICES, INC.  PURCHASE OF SHARES..........       8 
11 Greenway Plaza, Suite 1919                                                
Houston, Texas 77046-1173                REDEMPTION OF SHARES........       8  
                                                                             
                                         DIVIDENDS...................       9 
NO PERSON HAS BEEN AUTHORIZED TO                                             
GIVE ANY INFORMATION OR TO MAKE ANY      TAXES.......................       9 
REPRESENTATIONS NOT CONTAINED IN                                             
THIS PROSPECTUS IN CONNECTION WITH       NET ASSET VALUE.............      10 
THE OFFERING MADE BY THIS                                                    
PROSPECTUS, AND IF GIVEN OR MADE,        YIELD INFORMATION...........      10 
SUCH INFORMATION OR REPRESENTATIONS                                          
MUST NOT BE RELIED UPON AS HAVING        REPORTS TO SHAREHOLDERS.....      10 
BEEN AUTHORIZED BY THE FUND OR THE                                           
DISTRIBUTOR. THIS PROSPECTUS DOES        MANAGEMENT OF THE FUND......      11 
NOT CONSTITUTE AN OFFER IN ANY                                               
JURISDICTION TO ANY PERSON TO WHOM       GENERAL INFORMATION.........      12 
SUCH OFFERING MAY NOT LAWFULLY BE                                              
MADE.                                    APPENDIX....................     A-1  
                                         </TABLE>                             
=======================================  ====================================  


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