Exhibit 1(tt)

                              JANUS INVESTMENT FUND

                  CERTIFICATE REDESIGNATING JANUS MERCURY FUND

     The undersigned, being the Secretary of Janus Investment Fund, a
Massachusetts business trust with transferable shares (the "Trust"), being duly
authorized by a majority of the duly elected and qualified Trustees of the Trust
acting pursuant to Sections 3.6 and 4.1 of the Trust's Amended and Restated
Agreement and Declaration of Trust dated March 18, 2003, as further amended from
time to time (the "Declaration"), does hereby certify that, by affirmative vote
of all Trustees of the Trust present at a meeting of the Trustees, duly called,
convened and held on September 6, 2006, Janus Mercury Fund (the "Fund") was
redesignated as Janus Research Fund, such redesignation to be effective December
31, 2006.

     All of the current rights and preferences of the Fund remain in full force
and effect, as set forth in the Declaration.

     The undersigned further certifies that she has been duly authorized by the
Trustees of the Trust to take all necessary action to file a copy of this
Certificate with the Secretary of the Commonwealth of Massachusetts and at any
other place required by law or by the Declaration.

     IN WITNESS WHEREOF, I have hereunto set my hand as of the day and year set
forth opposite my signature below.


Dated: December 14, 2006                /s/ Stephanie Grauerholz-Lofton
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                                        Stephanie Grauerholz-Lofton, Secretary



                                 ACKNOWLEDGMENT

STATE OF COLORADO         )
                          ) ss.
CITY AND COUNTY OF DENVER )

     BEFORE ME, the undersigned authority, on this day personally appeared
Stephanie Grauerholz-Lofton, Secretary of Janus Investment Fund, a Massachusetts
business trust, who, after being first duly sworn, stated that she executed the
foregoing document for the consideration therein expressed and in the capacity
therein stated.

     SUBSCRIBED AND SWORN TO this 14th day of December, 2006

My Commission Expires:


6-22-07                                 /s/ Lisa A Neison
                                        ----------------------------------------
                                        Notary Public

                                        [Notary Seal]