Supplement to the currently effective Statements of Additional Information of
each of the Funds listed below:

Cash Management Fund Institutional       Cash Reserves Fund Institutional
Cash Reserve Fund, Inc.                  DWS Money Market Series
    Prime Series



The following replaces similar disclosure in the "Net Asset Value" section of
each Fund's Statements of Additional Information:

The net asset value ("NAV") per share of the Fund is calculated on each day on
which the Fund is open for business (each such day being a "Valuation Day"). The
Fund is open for business each day the New York Stock Exchange is open, as
described in the Fund's current prospectus. The NAV per share of the Fund is
computed by dividing the value of the Fund's assets (i.e., the value of the
Fund's investment in the Portfolio and any other assets) less all liabilities,
by the total number of shares of the Fund outstanding. Although there is no
guarantee, the Fund's NAV per share will normally be $1.00.

On each Valuation Day, the Portfolio determines its net value (i.e., the value
of the Portfolio's portfolio instruments and any other assets less all
liabilities). The Portfolio values its portfolio instruments at amortized cost,
which does not take into account unrealized capital gains or losses. This
involves initially valuing an instrument at its cost and thereafter assuming a
constant amortization to maturity of any discount or premium, regardless of the
impact of fluctuating interest rates on the market value of the instrument.
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 it sold the instrument.

Each investor in the Portfolio, including the Fund, may add to or reduce its
investment in the Portfolio on each Valuation Day. At the close of each such
Valuation Day, the value of each investor's beneficial interest in the Portfolio
will be determined by multiplying the net value of the Portfolio, as determined
by amortized cost, by the percentage, effective for that day, which represents
that investor's share of the aggregate beneficial interests in the Portfolio.
Any additions or withdrawals, which are to be effected as of the close of
business on that day, will then be effected. The percentage of the aggregate
beneficial interests in the Portfolio held by each investor in the Portfolio,
including the Fund will then be recomputed as the percentage equal to the
fraction (i) the numerator of which is the value of the investor's investment in
the Portfolio as of the close of business on such day plus or minus, as the case
may be, the amount of net additions to or withdrawals from such investor's
investment in the Portfolio effected as of the close of business on such day,
and (ii) the denominator of which is the aggregate net value of the Portfolio,
as determined by amortized cost, as of the close of business on such day plus or
minus, as the case may be, the amount of net additions to or withdrawals from
the aggregate investments in the Portfolio by all investors, including the Fund,
in the Portfolio. The percentage so determined for the Fund will then be applied
to determine the value of the Fund's interest in the Portfolio as of the close
of the following Valuation day.

The Board has established procedures reasonably designed to stabilize the Fund's
NAV per share at $1.00. Under the procedures, the Advisor will monitor and
notify the Board of circumstances where the Fund's NAV per share calculated
based on valuing the Fund's investment in the Portfolio and the Fund's other
assets using market valuations may deviate from the $1.00 per share calculated
based on valuing the Fund's investment in the Portfolio and the Fund's other
assets using amortized cost. If there were any deviation that the Board believed
would result in a material dilution or unfair result for investors or existing
shareholders, the Board would promptly consider what action, if any, should be
initiated. Such actions could include selling assets prior to maturity to
realize capital gains or losses; shortening average maturity of the portfolio;
withholding or reducing dividends; redeeming shares in kind; or valuing assets
based on market valuations. Because the Fund invests substantially all its
assets in the Portfolio, certain of these actions could be implemented at the
Portfolio level at the discretion of its Board.

Market valuations are obtained by using actual quotations provided by market
makers, estimates of market value, or values obtained from yield data relating
to classes of money market instruments published by reputable sources at the
mean between the bid and asked prices for the instruments. In accordance with
procedures approved by the

<PAGE>

Board, in the event market quotations are not readily available for certain
portfolio assets the fair value of such portfolio assets will be determined in
good faith by the Portfolio's Pricing Committee (or, in some cases, the Board's
Valuation Committee) based upon input from the Advisor or other third parties.
Additionally, for purposes of determining market valuations, through January 12,
2009, or such later date as extended by the SEC, certain portfolio assets may be
valued at amortized cost, unless the particular circumstances suggest that
amortized cost is no longer appropriate (e.g., there is an impairment of the
creditworthiness of the issuer). The use of amortized cost for purposes of
determining market valuations is limited to portfolio assets that (i) have a
remaining maturity of 60 days or less as set forth on the face of the
instrument; (ii) are considered First Tier Securities pursuant to SEC rules; and
(iii) are expected to be held to maturity.




               Please Retain this Supplement for Future Reference



December 1, 2008