Exhibit 11

[Letterhead]



August 8, 2006



Janus Investment Fund
151 Detroit Street
Denver, CO 80206

Ladies and Gentlemen:

         Reference is made to the registration statement on Form N-14 filed on
July 11, 2006 and Pre-Effective Amendment No. 1 to such registration statement
filed on August 8, 2006 (collectively, the "Registration Statement") with the
Securities and Exchange Commission with respect to shares of beneficial
interest, $.01 par value (the "Shares") of Janus Investment Fund, an
unincorporated association of the type commonly referred to as a Massachusetts
business trust (the "Trust"), representing interests in Janus Orion Fund, a
portfolio series of the Trust, to be issued pursuant to a certain Agreement and
Plan of Reorganization (the "Reorganization Agreement") by the Trust on behalf
of each of Janus Orion Fund and Janus Olympus Fund, also a portfolio series of
the Trust, dated as of July 6, 2006, described in the Registration Statement.

         We have examined such records, documents and other instruments and have
made such other examinations and inquiries as we have deemed necessary to enable
us to express the opinion set forth below.

         Based upon and subject to the foregoing, we are of the opinion that the
Shares, when issued in accordance with the terms of the Reorganization
Agreement, will be validly issued, fully paid and non-assessable by the Trust.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                                     Very truly yours,

                                                     /s/Goodwin Procter LLP

                                                     GOODWIN PROCTER LLP