<PAGE>
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON NOVEMBER 3, 1998
REGISTRATION NOS.: 333-29721
811-08265
- -------------------------------------------------------------------------------
- -------------------------------------------------------------------------------
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
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FORM N-1A
REGISTRATION STATEMENT
UNDER THE SECURITIES ACT OF 1933 [X]
PRE-EFFECTIVE AMENDMENT NO. [ ]
POST-EFFECTIVE AMENDMENT NO. 4 [X]
AND/OR
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY
ACT OF 1940 [X]
AMENDMENT NO. 5 [X]
----------------
MORGAN STANLEY DEAN WITTER S&P 500 INDEX FUND
(FORMERLY NAMED DEAN WITTER S&P 500 INDEX FUND)
(A MASSACHUSETTS BUSINESS TRUST)
(EXACT NAME OF REGISTRANT AS SPECIFIED IN CHARTER)
TWO WORLD TRADE CENTER
NEW YORK, NEW YORK 10048
(ADDRESS OF PRINCIPAL EXECUTIVE OFFICE)
REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (212) 392-1600
BARRY FINK, ESQ.
TWO WORLD TRADE CENTER
NEW YORK, NEW YORK 10048
(NAME AND ADDRESS OF AGENT FOR SERVICE)
COPY TO:
DAVID M. BUTOWSKY, ESQ.
GORDON ALTMAN BUTOWSKY
WEITZEN SHALOV & WEIN
114 WEST 47TH STREET
NEW YORK, NEW YORK 10036
----------------
APPROXIMATE DATE OF PROPOSED PUBLIC OFFERING:
As soon as practicable after this Post-Effective Amendment becomes effective.
----------------
IT IS PROPOSED THAT THIS FILING WILL BECOME EFFECTIVE (CHECK APPROPRIATE BOX)
X immediately upon filing pursuant to paragraph (b)
___ on (date) pursuant to paragraph (b)
___ 60 days after filing pursuant to paragraph (a)
___ on (date) pursuant to paragraph (a) of rule 485.
AMENDING THE PROSPECTUS AND UPDATING FINANCIAL STATEMENTS
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- --------------------------------------------------------------------------------
<PAGE>
MORGAN STANLEY DEAN WITTER S&P 500 INDEX FUND
CROSS-REFERENCE SHEET
FORM N-1A
<TABLE>
<CAPTION>
ITEM CAPTION
- ---- -------
PART A PROSPECTUS
- ------ ----------
<S> <C>
1. .......... Cover Page
2. .......... Summary of Fund Expenses; Prospectus Summary
3. .......... Financial Highlights; Performance Information
4. .......... Investment Objective and Policies; Risk Considerations and
Investment Practices; The Fund and Its Management; Cover
Page; Investment Restrictions; Prospectus Summary
5. .......... The Fund and Its Management; Back Cover; Investment
Objective and Policies
6. .......... Dividends, Distributions and Taxes; Additional Information
7. .......... Purchase of Fund Shares; Shareholder Services; Redemptions
and Repurchases
8. .......... Purchase of Fund Shares; Redemptions and Repurchases;
Shareholder Services
9. .......... Not Applicable
PART B STATEMENT OF ADDITIONAL INFORMATION
- ------ -----------------------------------
<S> <C>
10. .......... Cover Page
11. .......... Table of Contents
12. .......... The Fund and Its Management
13. .......... Investment Practices and Policies; Investment Restrictions;
Portfolio Transactions and Brokerage
14. .......... The Fund and Its Management; Trustees and Officers
15. .......... Trustees and Officers
16. .......... The Fund and Its Management; Purchase of Fund Shares;
Custodian and Transfer Agent; Independent Accountants
17. .......... Portfolio Transactions and Brokerage
18. .......... Description of Shares
19. .......... The Distributor; Purchase of Fund Shares; Redemptions and
Repurchases; Statement of Assets and Liabilities;
Shareholder Services
20. .......... Dividends, Distributions and Taxes
21. .......... The Distributor
22. .......... Performance Information
23. .......... Experts; Financial Statements
</TABLE>
PART C
- ------
Information required to be included in Part C is set forth under the
appropriate item, so numbered, in Part C of this Registration Statement.
<PAGE>
PART A
All disclosure contained in Part A (Prospectus) of Form N-1A of Post
Effective Amendment No. 3 to the Registration Statement of Morgan Stanley Dean
Witter S&P 500 Index Fund (the "Registrant"), filed with the Securities and
Exchange Commission on October 30, 1998, are herewith Incorporated by Reference
in this Post-Effective Amendment No. 4 to the Registration Statement of the
Registrant.
PART B
All disclosure contained in Part B (Statement of Additional Information)
of Form N-1A of Post-Effective Amendment No. 3 to the Registration Statement of
Morgan Stanley Dean Witter S&P Index Fund (the "Registrant"), filed with the
Securities and Exchange Commission on October 30, 1998, are herewith
Incorporated by Reference in this Post-Effective Amendment No. 4 to the
Registration Statement of the Registrant.
PART C
All disclosure contained in Part C of Form N-1A of Post-Effective
Amendment No. 3 to the Registration Statement of Morgan Stanley Dean Witter S&P
500 Index Fund (the "Registrant"), filed with the Securities and Exchange
Commission on October 30, 1998, are herewith Incorporated by Reference in this
Post-Effective Amendment No. 4 to the Registration Statement of the Registrant.
EXHIBITS
All exhibits, except Exhibit 27, to Part C of Form N-1A of Post-Effective
Amendment No. 3 to the Registration Statement of Morgan Stanley Dean Witter S&P
500 Index Fund (the "Registrant"), filed with the Securities and Exchange
Commission on October 30, 1998, are herewith Incorporated by Reference in this
Post-Effective Amendment No. 4 to the Registration Statement of the Registrant.
Exhibit 27 -- Financial Data Schedules, is an additional exhibit which was
inadvertently omitted from Post-Effective Amendment No. 3.
<PAGE>
SIGNATURES
Pursuant to the requirements of the Securities Act of 1933 and the
Investment Company Act of 1940, the Registrant certifies that it meets all of
the requirements for effectiveness of this Registration Statement pursuant to
Rule 485(b) under the Securities Act of 1933 and has duly caused this
Post-Effective Amendment to the Registration Statement to be signed on its
behalf by the undersigned, thereunto duly authorized, in the City of New York
and State of New York on the 3rd day of November, 1998.
MORGAN STANLEY DEAN WITTER S&P 500 INDEX FUND
By /s/ Barry Fink
---------------------------------
Barry Fink
Vice President and Secretary
Pursuant to the requirements of the Securities Act of 1933, this
Post-Effective Amendment No. 4 has been signed below by the following persons
in the capacities and on the dates indicated.
Signatures Title Date
---------- ----- ----
(1) Principal Executive Officer President, Chief
Executive Officer,
Trustee and Chairman
By /s/ Charles A. Fiumefreddo 11/03/98
---------------------------
Charles A. Fiumefreddo
(2) Principal Financial Officer Treasurer and Principal
Accounting Officer
By /s/ Thomas F. Caloia 11/03/98
---------------------------
Thomas F. Caloia
(3) Majority of the Trustees
Charles A. Fiumefreddo (Chairman)
Philip J. Purcell
By /s/ Barry Fink 11/03/98
---------------------------
Barry Fink
Attorney-in-Fact
Michael Bozic Manuel H. Johnson
Edwin J. Garn Michael E. Nugent
John R. Haire John L. Schroeder
Wayne E. Hedien
By /s/ David M. Butowsky 11/03/98
---------------------------
David M. Butowsky
Attorney-in-Fact
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<PAGE>
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<NUMBER> 01
<NAME> MSDW S&P 500 INDEX FUND CLASS A
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<NAME> MSDW S&P 500 INDEX FUND CLASS B
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<NUMBER-OF-SHARES-SOLD> 59,465,374
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<NUMBER> 03
<NAME> MSDW S&P 500 INDEX FUND CLASS C
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<NAME> MSDW S&P 500 INDEX FUND CLASS D
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