<PAGE>
SUPPLEMENT DATED DECEMBER 5, 2000
TO PROSPECTUS DATED MAY 1, 2000
OF
EQUITY GROWTH PORTFOLIO
FOCUS EQUITY PORTFOLIO
SMALL COMPANY GROWTH PORTFOLIO
VALUE EQUITY PORTFOLIO
TECHNOLOGY PORTFOLIO
PORTFOLIOS OF THE
MORGAN STANLEY DEAN WITTER INSTITUTIONAL FUND, INC.
P.O. BOX 2798
BOSTON, MASSACHUSETTS
02208-2798
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The Prospectus is hereby amended and supplemented to reflect a change in the
universe of companies the Value Equity Portfolio invests in and the comparative
index for the Portfolio.
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The paragraph entitled "Process" on page 4 of the Prospectus is deleted and
replaced with the following:
PROCESS
MSDW Investment Management establishes a universe comprised of approximately
1000 companies that exhibit defined value characteristics. The selection process
focuses on companies with distinctively below average price-to-earnings and
price-to-book value ratios and high dividend yields. MSDW Investment Management
conducts additional fundamental analysis to ascertain financial soundness. The
Portfolio then purchases securities of companies that research indicates sell
below their estimated value. The Portfolio will typically sell securities when
prices revert to MSDW Investment Management's estimated value.
------------------------
The Russell 1000 Value Index is being added as the primary comparative index for
the Value Equity Portfolio. The S&P 500 Index will remain as a secondary
comparative index. MSDW Investment Management believes that the Russell 1000
Value Index is more representative of the value-oriented companies in the Value
Equity Portfolio. Accordingly, the chart on page 4 is hereby deleted and
replaced with the following:
AVERAGE ANNUAL TOTAL RETURN (FOR THE YEAR ENDED DECEMBER 31, 1999)
<TABLE>
<CAPTION>
CLASS A CLASS B
(COMMENCED (COMMENCED RUSSELL 1000 VALUE
OPERATIONS ON OPERATIONS ON INDEX* S&P 500 INDEX**
JANUARY 31, 1990) JANUARY 2, 1996) CLASS A CLASS B CLASS A CLASS B
<S> <C> <C> <C> <C> <C> <C>
----------------------------------------------------------------------------------------------------------------
PAST ONE YEAR 11.63% 11.22% 7.35% 7.35% 21.04% 21.04%
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PAST FIVE YEARS 20.22% N/A 23.08% N/A 28.55% N/A
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SINCE INCEPTION 13.93% 16.53% 16.46% 19.36% 19.21% 26.18%
</TABLE>
THE BAR CHART AND TABLE ABOVE SHOW THE PERFORMANCE OF THE PORTFOLIO YEAR-BY-YEAR
AND AS AN AVERAGE OVER DIFFERENT PERIODS OF TIME. TOGETHER, THE BAR CHART AND
TABLE DEMONSTRATE THE VARIABILITY OF PERFORMANCE OVER TIME AND PROVIDE AN
INDICATION OF THE RISKS OF INVESTING IN THE PORTFOLIO. IN ADDITION, THE TABLE
COMPARES THE PERFORMANCE OF THE PORTFOLIO TO INDICES OF SIMILAR SECURITIES. AN
INDEX IS A HYPOTHETICAL MEASURE OF PERFORMANCE BASED ON THE UPS AND DOWNS OF
SECURITIES THAT MAKE UP A PARTICULAR MARKET. THE INDICES DO NOT SHOW ACTUAL
INVESTMENT RETURNS OR REFLECT PAYMENT OF MANAGEMENT OR BROKERAGE FEES, WHICH
WOULD LOWER THE INDICES' PERFORMANCE. THE TABLE SEPARATELY COMPARES CLASS A AND
CLASS B SHARES TO EACH INDEX SO THAT YOU CAN COMPARE PERFORMANCE FOR EACH CLASS
FROM ITS COMMENCEMENT DATE. THE INDICES THEMSELVES DO NOT ACTUALLY HAVE TWO
CLASSES. HOW THE PORTFOLIO HAS PERFORMED IN THE PAST DOES NOT NECESSARILY
INDICATE HOW THE PORTFOLIO WILL PERFORM IN THE FUTURE.
*THE RUSSELL 1000 VALUE INDEX IS AN UNMANAGED INDEX OF THOSE COMPANIES IN THE
RUSSELL 1000 INDEX WITH LOWER PRICE-TO-BOOK RATIOS AND LOWER FORECASTED
GROWTH VALUES.
**THE S&P 500 INDEX IS COMPRISED OF THE STOCKS OF 500 LARGE-CAP U.S. COMPANIES
WITH MARKET CAPITALIZATION OF $1 BILLION OR MORE. THESE 500 COMPANIES
REPRESENT APPROXIMATELY 100 INDUSTRIES, CHOSEN MAINLY FOR MARKET SIZE,
LIQUIDITY AND INDUSTRY GROUP REPRESENTATION.
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PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE
