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                                                                  Exhibit 4(aaa)

                                  AMENDMENT TO

                              JANUS ADVISER SERIES

                          INVESTMENT ADVISORY AGREEMENT

                            JANUS ADVISER GROWTH FUND

      THIS AMENDMENT is made this 28th day of February, 2005, between JANUS
ADVISER SERIES, a Delaware statutory trust (the "Trust"), and JANUS CAPITAL
MANAGEMENT LLC, a Delaware limited liability company ("JCM").

                                   WITNESSETH

      WHEREAS, the Trust and JCM are parties to an Investment Advisory Agreement
on behalf of Janus Adviser Growth Fund (the "Fund"), dated July 1, 2004 (the
"Agreement");

      WHEREAS, the parties desire to amend the Agreement as set forth in greater
detail below;

      WHEREAS, pursuant to Section 12 of the Agreement, any amendment to the
Agreement is subject to approval (i) by a majority of the Trustees, including a
majority of the Trustees who are not interested persons (as that phrase is
defined in Section 2(a)(19) of the Investment Company Act of 1940, as amended
(the "1940 Act")) of any party to the Agreement and, if required by applicable
law, (ii) by the affirmative vote of a majority of the outstanding voting
securities of the Fund (as that phrase is defined in Section 2(a)(42) of the
1940 Act);

      WHEREAS, the parties have obtained Trustee approval as set forth above,
and the parties agree that a shareholder vote is not required to amend the
Agreement; and

      WHEREAS, the name of Janus Adviser Growth Fund has been changed to Janus
Adviser Large Cap Growth Fund;

      NOW, THEREFORE, in consideration of the premises and of the mutual
agreements set forth below, the parties agree to amend the Agreement as follows:

      1. All references to "Janus Adviser Growth Fund" shall be replaced with
"Janus Adviser Large Cap Growth Fund."

      2. The parties acknowledge that the Agreement, as amended, remains in full
force and effect as of the date of this Amendment, and that this Amendment,
together with the Agreement and any prior amendments, contains the entire
understanding and the full and complete agreement of the parties and supercedes
and replaces any prior understandings and agreements among the parties
respecting the subject matter hereof.

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      3. This Amendment may be contemporaneously executed in two or more
counterparts, each of which shall be deemed an original but all of which
together shall constitute one and the same instrument.

      IN WITNESS WHEREOF, the parties have caused their duly authorized officers
to execute this Amendment as of the date first above written.

                                     JANUS CAPITAL MANAGEMENT LLC

                                     By: /s/ Loren M. Starr
                                         ---------------------------------------
                                         Loren M. Starr, Chief Financial Officer
                                         and Senior Vice President

                                     JANUS ADVISER SERIES

                                     By: /s/ Girard C. Miller
                                         ---------------------------------------
                                         Girard C. Miller, President and Chief
                                         Executive Officer