The following certification is provided by the undersigned Principal Executive
Officer and Principal Financial Officer of Registrant on the basis of such
officers' knowledge and belief for the sole purpose of complying with 18 U.S.C.
Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of
2002.

                                 Certification

In connection with the Semi-annual Report of Janus Investment Fund (the
"Registrant") on Form N-CSR for the period ended April 30, 2004, as filed with
the Securities and Exchange Commission on June 29, 2004 (the "Report"), we,
Girard C. Miller, Principal Executive Officer of the Registrant, and Loren M.
Starr, Principal Financial Officer of the Registrant hereby certify, pursuant to
18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, that:

(1)  The Report fully complies with the  requirements of Sections 13(a) or 15(d)
     of the Securities Exchange Act of 1934, as amended; and

(2)  The information contained in the Report fairly presents, in all material
     respects, the financial condition and results of operations of the
     Registrant.



/s/ Girard C. Miller
Principal Executive Officer of Janus Investment Fund
June 29, 2004


/s/ Loren M. Starr
Principal Financial Officer of Janus Investment Fund
June 29, 2004