Insmed Incorporated
INSMED INC (Form: SC 13G, Received: 02/15/2001 13:15:18)      
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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Ammendment No. )

Insmed Inc.
(Name of Issuer)

Common Shares
(Title of Class of Securities)

457669208
(CUSIP Number)

December 31, 2000
(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:

/_X_/ Rule 13d-1(b)
/___/ Rule 13d-1(c)
/___/ Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.
SEC 1745 (3-98) Page 1 of 9


 
CUSIP No. 457669208                             13G                             Page 2 of 9 Pages

----------------------------------------------------------------
1       NAME OF REPORTING PERSONS
        IRS IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

        RS Investment Management Co. LLC
----------------------------------------------------------------
2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions)
        (a)/  /
        (b)/  /
----------------------------------------------------------------
3       SEC USE ONLY

----------------------------------------------------------------
4       CITIZENSHIP OR PLACE OF ORGANIZATION

        Delaware
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          NUMBER OF     5       SOLE VOTING POWER
           SHARES                       -0-
        BENEFICIALLY            ---------------------------------------
          OWNED BY              6       SHARED VOTING POWER
            EACH                        1,805,700
         REPORTING              ---------------------------------------
           PERSON               7       SOLE DISPOSITIVE POWER
            WITH                        -0-
                                        ---------------------------------------
                                8       SHARED DISPOSITIVE POWER
                                        1,805,700
----------------------------------------------------------------
9       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
        1,805,700
----------------------------------------------------------------
10      CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See
Instructions)

----------------------------------------------------------------
11      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
        5.5%
----------------------------------------------------------------
12      TYPE OF REPORTING PERSON (See Instructions)
        OO, HC
----------------------------------------------------------------


 
CUSIP No. 457669208                             13G                             Page 3 of 9 Pages

----------------------------------------------------------------
1       NAME OF REPORTING PERSONS
        IRS IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

        RS Investment Management, L.P.
----------------------------------------------------------------
2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions)
        (a)/  /
        (b)/  /
----------------------------------------------------------------
3       SEC USE ONLY

----------------------------------------------------------------
4       CITIZENSHIP OR PLACE OF ORGANIZATION

        California
----------------------------------------------------------------
          NUMBER OF     5       SOLE VOTING POWER
           SHARES                       -0-
        BENEFICIALLY            ---------------------------------------
          OWNED BY              6       SHARED VOTING POWER
            EACH                        1,805,700
         REPORTING              ---------------------------------------
           PERSON               7       SOLE DISPOSITIVE POWER
            WITH                        -0-
                                        ---------------------------------------
                                8       SHARED DISPOSITIVE POWER
                                        1,805,700
----------------------------------------------------------------
9       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
        1,805,700
----------------------------------------------------------------
10      CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (See
Instructions)

----------------------------------------------------------------
11      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
        5.5%
----------------------------------------------------------------
12      TYPE OF REPORTING PERSON (See Instructions)
        PN, IA
----------------------------------------------------------------
CUSIP No. 457669208                             13G                     Page 4 of 9 Pages

ITEM 1.

     (a)  The name of the issuer is Insmed (the "Issuer").

     (b)  The principal executive office of the Issuer is located at: 800
E. Leigh St, Richmond VA 23219.


ITEM 2.

     (a-c)  See Annex I for information on the persons filing this
statement (collectively, the "Filers")

     (d)  This statement relates to shares of common stock of the Issuer
(the "Stock").

     (e)  The CUSIP number of the Stock is 457669208.


 
CUSIP No. 457669208                             13G                     Page 5 of 9 Pages

ITEM 3.  If this statement is filed pursuant to rule 240.13d-1(b) or
240.13d-2(b) or (c), check whether the person filing is a:

        (a)     ___     Broker or dealer registered under section 15 of the Act (15
U.S.C. 78o).

        (b)     ___     Bank as defined in section 3(a)(6) of the Act (15 U.S.C.
78c).

        (c)     ___     Insurance company as defined in section 3(a)(19) of the Act
(15 U.S.C. 78c).

        (d)     ___     Investment company registered under section 8 of the
Investment Company Act of 1940 (15 U.S.C. 80a-8).

        (e)     ___     An investment adviser in accordance with 240.13d-
1(b)(1)(ii)(E).

        (f)     ___     An employee benefit plan or endowment fund in accordance
with 240.13d-1(b)(1)(ii)(F).

        (g)     ___     A parent holding company or control person in accordance
with 240.13d-1(b)(1)(ii)(G)

        (h)     ___     A savings association as defined in section 3(b) of the
Federal Deposit Insurance Act (12 U.S.C. 1813).

        (i)     ___     A church plan that is excluded from the definition of an
investment company under section 3(c)(14) of the Investment Company Act of
1940 (15 U.S.C. 80a-3).

        (j)     _X_     Group, in accordance with section 240.13d-1(b)(1)(ii)(J)


 
CUSIP No. 457669208                             13G                     Page 6 of 9 Pages

ITEM 4.  OWNERSHIP

See Items 5-9 and 11 on the cover page for each Filer.


ITEM 5.  OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS

If this statement is being filed to report the fact that as of the date
hereof the reporting person has ceased to be the beneficial owner of more
than five percent of the class of securities, check the following /___/.


ITEM 6.  OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON

The Filer is a registered investment adviser whose clients have the right
to receive or the power to direct the receipt of dividends from, or the
proceeds from the sale of, the Stock.  No individual client's holdings of
the Stock are more than five percent of the outstanding Stock.


 
CUSIP No. 457669208                             13G                     Page 7 of 9 Pages


ITEM 7.  IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED
THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY

Not applicable.

ITEM 8.  IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP

See Annex I

ITEM 9.  NOTICE OF DISSOLUTION OF GROUP

Not applicable.

ITEM 10.  CERTIFICATION

By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were acquired and are held in the ordinary
course of business and were not acquired and are not held for the purpose
of or with the effect of changing or influencing the control of the issuer
of the securities and were not acquired and are not held in connection with
or as a participant in any transaction having that purpose or effect.



                                                SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete
and correct.

Dated:  February 8, 2001

RS INVESTMENT MANAGEMENT CO. LLC
        By:  /s/        G. Randall Hecht
                        G. Randall Hecht
                        Chief Executive Officer

RS INVESTMENT MANAGEMENT, LP.
        By:      /s/    G. Randall Hecht
                        G. Randall Hecht
                        Chief Executive Officer


CUSIP No. 457669208                             13G                     Page 8 of 9 Pages

EXHIBIT A

JOINT FILING AGREEMENT

The undersigned hereby agree that they are filing this statement jointly
pursuant to Rule 13d-1(f)(1).  Each of them is responsible for the timely
filing of the Schedule 13G and any amendments thereto, and for the
completeness and accuracy of the information concerning such person
contained therein; but none of them is responsible for the completeness or
accuracy of the information concerning the other persons making the filing,
unless such person knows or has reason to believe that such information is
accurate.

Dated:  February 8, 2001

RS INVESTMENT MANAGEMENT CO. LLC
        By:  /s/        G. Randall Hecht
                        G. Randall Hecht
                        Chief Executive Officer

RS INVESTMENT MANAGEMENT, LP.
        By:      /s/    G. Randall Hecht
                        G. Randall Hecht
                        Chief Executive Officer


 
CUSIP No. 457669208                             13G                     Page 9 of 9 Pages

Annex I

The filers are:

I.      (a)     RS Investment Management Co. LLC, is a Delaware Limited Liability
     Company.
(b) holding company

II.     (a)     RS Investment Management, L.P. is a California Limited
Partnership
(b) registered investment adviser