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                                                                    Exhibit 4(t)

                              JANUS ADVISER SERIES.

                          INVESTMENT ADVISORY AGREEMENT

                        JANUS ADVISER MID CAP VALUE FUND

      THIS INVESTMENT ADVISORY AGREEMENT (the "Agreement") is made this 10th day
of December, 2002, between Janus Adviser Series, a Delaware business trust (the
"Trust"), and JANUS CAPITAL MANAGEMENT LLC, a Delaware limited liability company
("JCM").

                              W I T N E S S E T H:

      WHEREAS, the Trust is registered as an open-end management investment
company under the Investment Company Act of 1940, as amended (the "1940 Act"),
and has registered its shares for public offering under the Securities Act of
1933, as amended (the "1933 Act"); and

      WHEREAS, the Trust is authorized to create separate funds, each with its
own separate investment portfolio of which the beneficial interests are
represented by a separate series of shares; one of such funds created by the
Trust being designated as the Janus Adviser Mid Cap Value Fund (the "Fund"); and

      WHEREAS, the Trust and JCM deem it mutually advantageous that JCM should
be appointed as investment adviser to the Fund.

      NOW, THEREFORE, the parties agree as follows:

      1. Appointment. The Trust hereby appoints JCM as investment adviser and
manager with respect to the Fund for the period and on the terms set forth in
this Agreement. JCM hereby accepts such appointment and agrees to render the
services herein set forth, for the compensation herein provided.

      2. Investment Advisory Services. JCM shall determine the securities or
other assets to be purchased, sold or held and shall place orders for the
purchase or sale of such securities or other assets with brokers, dealers or
others. JCM shall furnish continuous advice and recommendations to the Fund as
to the acquisition, holding, or disposition of any or all of the securities or
other assets which the Fund may own or contemplate acquiring from time to time.
JCM shall give due consideration to the investment policies and restrictions and
the other statements concerning the Fund in the Trust Instrument, bylaws, and
registration statements under the 1940 Act and the 1933 Act, and to the
provisions of the Internal Revenue Code, as amended from time to time,
applicable to the Fund as a regulated investment company. In addition, JCM shall
cause its officers to attend meetings and furnish oral or written reports, as
the Trust may reasonably require, in order to keep the Trustees and appropriate
officers of the Trust fully informed as to the condition of the investment
portfolio of the Fund, the investment recommendations of JCM, and the investment
considerations which have given rise to those recommendations. Subject to the
approval of the Trustees of the Trust and, if required, the shareholders of the
Fund, JCM is authorized to engage one or more subadvisers in connection
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with JCM's duties and responsibilities under this Agreement, which subadvisers
may be affiliates of JCM.

      3. Other Services. JCM is hereby authorized (to the extent the Trust has
not otherwise contracted) but not obligated (to the extent it so notifies the
Trustees at least 60 days in advance), to perform (or arrange for the
performance by duly appointed subadvisers or affiliates of) the management and
administrative services necessary for the operation of the Fund. JCM is
specifically authorized, on behalf of the Trust, to conduct relations with
custodians, depositories, transfer and pricing agents, accountants, attorneys,
underwriters, brokers and dealers, corporate fiduciaries, insurance company
separate accounts, insurers, banks and such other persons in any such other
capacity deemed by JCM to be necessary or desirable. JCM shall generally monitor
and report to Fund officers the Fund's compliance with investment policies and
restrictions as set forth in the currently effective prospectus and statement of
additional information relating to the shares of the Fund under the Securities
Act of 1933, as amended. JCM shall make reports to the Trustees of its
performance of services hereunder upon request therefor and furnish advice and
recommendations with respect to such other aspects of the business and affairs
of the Fund as it shall determine to be desirable. JCM is also authorized,
subject to review by the Trustees, to furnish such other services as JCM shall
from time to time determine to be necessary or useful to perform the services
contemplated by this Agreement.

      4. Obligations of Trust. The Trust shall have the following obligations
under this Agreement:

            (a)   to keep JCM continuously and fully informed as to the
                  composition of its investment portfolio and the nature of all
                  of its assets and liabilities from time to time;

            (b)   to furnish JCM with a certified copy of any financial
                  statement or report prepared for it by certified or
                  independent public accountants and with copies of any
                  financial statements or reports made to its shareholders or to
                  any governmental body or securities exchange;

            (c)   to furnish JCM with any further materials or information which
                  JCM may reasonably request to enable it to perform its
                  function under this Agreement;

            (d)   to compensate JCM for its services and reimburse JCM for its
                  expenses incurred hereunder in accordance with the provisions
                  hereof; and

            (e)   to compensate any subadviser engaged by JCM pursuant to the
                  authority granted in Section 1 hereof.

      5. Compensation. The Trust shall pay to JCM for its investment advisory
services a fee, calculated and payable for each day that this Agreement is in
effect, of 1/365 of 0.65% of the daily closing net asset value of the Fund
(1/366 of 0.65% of the daily closing net asset value of the Fund in a leap year)
provided that any amounts due pursuant to Section 4(e) above shall be
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paid directly to such subadviser by the Fund and shall reduce the amount payable
to JCM hereunder.

      6. Expenses Borne by JCM. In addition to the expenses which JCM may incur
in the performance of its investment advisory functions under this Agreement,
and the expenses which it may expressly undertake to incur and pay under other
agreements with the Trust or otherwise, JCM shall incur and pay the following
expenses relating to the Fund's operations without reimbursement from the Fund:

            (a)   Reasonable compensation, fees and related expenses of the
                  Trust's officers and its Trustees, except for such Trustees
                  who are not interested persons of JCM; and

            (b)   Rental of offices of the Trust.

      7. Expenses Borne by the Trust. The Trust assumes and shall pay all
expenses incidental to its organization, operations and business not
specifically assumed or agreed to be paid by JCM pursuant to Sections 3 and 6
hereof, including, but not limited to, investment adviser fees; any
compensation, fees, or reimbursements which the Trust pays to its Trustees who
are not interested persons of JCM; compensation of the Fund's custodian,
transfer agent, registrar and dividend disbursing agent; legal, accounting,
audit and printing expenses; administrative, clerical, recordkeeping and
bookkeeping expenses; brokerage commissions and all other expenses in connection
with execution of portfolio transactions (including any appropriate commissions
paid to JCM or its affiliates for effecting exchange listed, over-the-counter or
other securities transactions); interest; all federal, state and local taxes
(including stamp, excise, income and franchise taxes); costs of stock
certificates and expenses of delivering such certificates to purchasers thereof;
expenses of local representation in Delaware; expenses of shareholders' meetings
and of preparing, printing and distributing proxy statements, notices, and
reports to shareholders; expenses of preparing and filing reports and tax
returns with federal and state regulatory authorities; all expenses incurred in
complying with all federal and state laws and the laws of any foreign country
applicable to the issue, offer, or sale of shares of the Fund, including, but
not limited to, all costs involved in the registration or qualification of
shares of the Fund for sale in any jurisdiction, the costs of portfolio pricing
services and compliance systems, and all costs involved in preparing, printing
and mailing prospectuses and statements of additional information to fund
shareholders; and all fees, dues and other expenses incurred by the Trust in
connection the membership of the Trust in any trade association or other
investment company organization.

      8. Termination. This Agreement may be terminated at any time, without
penalty, by the Trustees of the Trust, or by the shareholders of the Fund acting
by vote of at least a majority of its outstanding voting securities, provided in
either case that sixty (60) days advance written notice of termination be given
to JCM at its principal place of business. This Agreement may be terminated by
JCM at any time, without penalty, by giving sixty (60) days advance written
notice of termination to the Trust, addressed to its principal place of
business. The Trust agrees that, consistent with the terms of the Trust
Instrument, the Trust shall cease to use the name "Janus" in connection with the
Fund as soon as reasonably practicable following any termination of this
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Agreement if JCM does not continue to provide investment advice to the Fund
after such termination.

      9. Assignment. This Agreement shall terminate automatically in the event
of any assignment of this Agreement.

      10. Term. This Agreement shall continue in effect until July 1, 2004,
unless sooner terminated in accordance with its terms, shall continue in effect
from year to year thereafter only so long as such continuance is specifically
approved at least annually by the vote of a majority of the Trustees of the
Trust who are not parties hereto or interested persons of any such party, cast
in person at a meeting called for the purpose of voting on the approval of the
terms of such renewal, and by either the Trustees of the Trust or the
affirmative vote of a majority of the outstanding voting securities of the Fund.
The annual approvals provided for herein shall be effective to continue this
Agreement from year to year if given within a period beginning not more than
ninety (90) days prior to July 1 of each applicable year, notwithstanding the
fact that more than three hundred sixty-five (365) days may have elapsed since
the date on which such approval was last given.

      11. Amendments. This Agreement may be amended by the parties only if such
amendment is specifically approved (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 1940 Act) of JCM 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).

      12. Other Series. The Trustees shall determine the basis for making an
appropriate allocation of the Trust's expenses (other than those directly
attributable to the Fund) between the Fund and the other series of the Trust.

      13. Limitation of Personal Liability. All the parties hereto acknowledge
and agree that all liabilities of the Trust arising, directly or indirectly,
under this Agreement, of any and every nature whatsoever, shall be satisfied
solely out of the assets of the Fund and that no Trustee, officer or holder of
shares of beneficial interest of the Trust shall be personally liable for any of
the foregoing liabilities. The Trust Instrument describes in detail the
respective responsibilities and limitations on liability of the Trustees,
officers and holders of shares of beneficial interest of the Trust.

      14. Limitation of Liability of JCM. JCM shall not be liable for any error
of judgment or mistake of law or for any loss arising out of any investment or
for any act or omission taken with respect to the Trust, except for willful
misfeasance, bad faith or gross negligence in the performance of its duties, or
by reason of reckless disregard of its obligations and duties hereunder and
except to the extent otherwise provided by law. As used in this Section 14,
"JCM" shall include any affiliate of JCM performing services for the Trust
contemplated hereunder and directors, officers and employees of JCM and such
affiliates.
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      15. Activities of JCM. The services of JCM to the Trust hereunder are not
to be deemed to be exclusive, and JCM and its affiliates are free to render
services to other parties. It is understood that trustees, officers and
shareholders of the Trust are or may become interested in JCM as directors,
officers and shareholders of JCM, that directors, officers, employees and
shareholders of JCM are or may become similarly interested in the Trust, and
that JCM may become interested in the Trust as a shareholder or otherwise.

      16. Certain Definitions. The terms "vote of a majority of the outstanding
voting securities," "assignment" and "interested persons" when used herein,
shall have the respective meanings specified in the 1940 Act, as now in effect
or hereafter amended, and the rules and regulations thereunder, subject to such
orders, exemptions and interpretations as may be issued by the Securities and
Exchange Commission under said Act and as may be then in effect.

      17. Governing Law. This Agreement shall be construed in accordance with
the laws of the State of Colorado (without giving effect to the conflicts of
laws principles thereof) and the 1940 Act. To the extent that the applicable
laws of the State of Colorado conflict with the applicable provisions of the
1940 Act, the latter shall control.

      IN WITNESS WHEREOF, the parties have caused their duly authorized officers
to execute this Investment Advisory Agreement as of the date and year first
above written.

                                          JANUS CAPITAL MANAGEMENT LLC


                                          By:
                                             -----------------------------------
                                             Thomas A. Early, Vice President


                                          JANUS ADVISER SERIES


                                          By:
                                             -----------------------------------
                                             Kelley Abbott Howes, Vice President