<PAGE>
As Filed With the Securities and Exchange Commission on December 1, 2000
File No. 33-23166
811-5624
----------------------------------------------------------------------------
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
----------------
FORM N-1A
REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 / /
POST-EFFECTIVE AMENDMENT NO. 45 /X/
and
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 / /
AMENDMENT NO. 46 /X/
MORGAN STANLEY DEAN WITTER INSTITUTIONAL FUND, INC.
----------------------------------------------------
(Exact Name of Registrant as Specified in Charter)
1221 Avenue of the Americas
New York, New York 10020
------------------------------------------
(Address of Principal Executive Offices) (Zip Code)
Registrant's Telephone Number, including Area Code: (800) 548-7786
--------------
Harold J. Schaaff, Jr., Esq.
Morgan Stanley Dean Witter Investment Management Inc.
1221 Avenue of the Americas, New York, New York 10020
-----------------------------------------------------------------
(Name and Address of Agent for Service)
Copy to:
<TABLE>
<CAPTION>
<S> <C>
Arthur Lev Esq. Richard W. Grant, Esq.
Morgan Stanley Dean Witter Investment Management Inc. Morgan, Lewis & Bockius LLP
1221 Avenue of the Americas 1701 Market Street
New York, NY 10020 Philadelphia, PA 19103
</TABLE>
--------------------------------------------------------------------------------
It is proposed that this filing will become effective (check appropriate box)
immediately upon filing pursuant to paragraph (b)
----
X on January 2, 2001 pursuant to paragraph (b)(1)(iii)
----
60 days after filing pursuant to paragraph (a)(1)
----
75 days after filing pursuant to paragraph (a)(2)
----
on [ date] pursuant to paragraph (a) of Rule 485.
----
--------------------------------------------------------------------------------
<PAGE>
The Fund's Prospectus relating to the Emerging Markets Advisory
Portfolio of the Fund is hereby incorporated by reference to Post-Effective
Amendment No. 44 to the Registrant's Registration Statement on Form N-1A,
filed with the Securities and Exchange Commission via EDGAR (Accession No.
0000912057-00-041887) on September 19, 2000.
The Fund's Statement of Additional Information relating to the Emerging
Markets Advisory Portfolio of the Fund is hereby incorporated by reference to
Post-Effective Amendment No. 44 to the Registrant's Registration Statement on
Form N-1A, filed with the Securities and Exchange Commission via EDGAR
(Accession No. 0000912057-00-041887) on September 19, 2000.
The Fund's Part C is hereby incorporated by reference to Post-Effective
Amendment No. 44 to the Registrant's Registration Statement on Form N-1A, filed
with the Securities and Exchange Commission via EDGAR (Accession No.
0000912057-00-041887) on September 19, 2000.
<PAGE>
SIGNATURES
Pursuant to the requirements of the Securities Act of 1933, as
amended (the "1933 Act"), and the Investment Company Act of 1940, as amended,
the Registrant has duly caused this Amendment to its 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 December 1, 2000.
MORGAN STANLEY DEAN WITTER INSTITUTIONAL FUND, INC.
By: /s/ Harold J. Schaaff, Jr.
--------------------------
Harold J. Schaaff, Jr.
President
Pursuant to the requirements of the 1933 Act, this Amendment to the
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.
<TABLE>
<CAPTION>
SIGNATURE TITLE DATE
------------------------------- ----------------------------- ---------
<S> <C> <C>
/s/ Harold J. Schaaff, Jr. President December 1, 2000
------------------------------- (Principal Executive
Harold J. Schaaff, Jr. Officer)
*/s/ Barton M. Biggs Director (Chairman) December 1, 2000
-------------------------------
Barton M. Biggs
*/s/ Fergus Reid Director December 1, 2000
-------------------------------
Fergus Reid
*/s/ Frederick O. Robertshaw Director December 1, 2000
-------------------------------
Frederick O. Robertshaw
*/s/ Andrew McNally, IV Director December 1, 2000
-------------------------------
Andrew McNally IV
*/s/ John D. Barrett, II Director December 1, 2000
-------------------------------
John D. Barrett II
*/s/ Gerard E. Jones Director December 1, 2000
-------------------------------
Gerard E. Jones
*/s/ Samuel T. Reeves Director December 1, 2000
-------------------------------
Samuel T. Reeves
*/s/ Graham E. Jones Director December 1, 2000
-------------------------------
Graham E. Jones
*/s/ John A. Levin Director December 1, 2000
-------------------------------
John A. Levin
*/s/ William G. Morton, Jr. Director December 1, 2000
-------------------------------
William G. Morton, Jr.
/s/ Belinda A. Brady Treasurer December 1, 2000
-------------------------------
Belinda A. Brady
</TABLE>
*By: /s/ Harold J. Schaaff, Jr.
--------------------------
Harold J. Schaaff, Jr.
Attorney-In-Fact
