Janus Investment Fund

                          Perkins Small Cap Value Fund

                         Supplement dated April 20, 2010
                       to Currently Effective Prospectuses

Effective May 28, 2010, Perkins Small Cap Value Fund (the "Fund") is closed to
new investors. Current investors may continue to invest in the Fund, as well as
reinvest any dividends or capital gains distributions. However, once an account
is closed, additional investments in the Fund will not be accepted unless you
meet the criteria outlined below. Please contact your financial intermediary (or
Janus if you hold shares directly with Janus Capital) for further details.

Accordingly, the following information supplements the "SHAREHOLDER'S GUIDE" (or
"SHAREHOLDER'S MANUAL" if you hold shares directly with Janus Capital) section
of the Prospectus:

     CLOSED FUND POLICIES -- PERKINS SMALL CAP VALUE FUND
     The Fund has limited sales of its shares because Janus Capital and the
     Trustees believe continued sales may adversely affect the Fund's ability to
     achieve its investment objective. Sales to new investors have generally
     been discontinued and financial intermediaries may not open new accounts
     with the Fund or add new investors to existing omnibus accounts. Investors
     who meet certain criteria described below, however, may be able to purchase
     shares of the Fund. You may be required to demonstrate eligibility to
     purchase shares of the Fund before your investment is accepted. If you are
     a current Fund shareholder and close an existing Fund account, you will not
     be able to make additional investments in the Fund unless you meet one of
     the specified criteria. The Fund may resume sales of its shares at some
     future date, but it has no present intention to do so.

     Investors who meet the following criteria may be able to invest in the
     Fund: (i) existing shareholders invested in the Fund are permitted to
     continue to purchase shares through their existing Fund accounts and to
     reinvest any dividends or capital gains distributions in such accounts,
     absent highly unusual circumstances; (ii) discretionary investment advisers
     may continue to invest in the Fund through an existing omnibus account at a
     financial institution and/or intermediary on behalf of clients who are
     current Fund shareholders; (iii) under certain circumstances, all or a
     portion of the shares held in a closed Fund account may be reallocated to a
     different form of ownership; this may include, but is not limited to,
     mandatory retirement distributions, legal proceedings, estate settlements,
     and the gifting of Fund shares; (iv) it is expected that existing or new
     participants in employer-sponsored retirement plans, including



     employees of Janus Capital Group Inc. ("JCGI") and any of its subsidiaries
     covered under the JCGI retirement plan, that currently offer the Fund as an
     investment option may direct contributions to the Fund through their plan,
     regardless of whether the participant invested in such Fund prior to its
     closing; (v) certain new retirement plans investing directly with Janus or
     through intermediaries that offered the Fund prior to the Fund's closing;
     (vi) Janus Capital encourages its employees to own shares of the Janus
     funds, and as such, upon prior approval, employees of Janus Capital and its
     affiliates may open new accounts in the closed Fund; Trustees of the Janus
     funds and directors of JCGI may also open new accounts in the closed Fund;
     (vii) Janus "fund of funds," which is a fund that primarily invests in
     other Janus mutual funds may invest in the Fund; (viii) sponsors of certain
     wrap programs with existing accounts in the Fund would be able to continue
     to invest in the Fund on behalf of new customers; and (ix) in the case of
     certain mergers or reorganizations, retirement plans may be able to add the
     closed Fund as an investment option and sponsors of certain wrap programs
     with existing accounts in the Fund would be able to continue to invest in
     the Fund on behalf of new customers. Such mergers, reorganizations,
     acquisitions, or other business combination are those in which one or more
     companies involved in such transaction currently offers the Fund as an
     investment option, and any company that as a result of such transaction
     becomes affiliated with the company currently offering the Fund (as a
     parent company, subsidiary, sister company, or otherwise). Such companies
     may request to add the Fund as an investment option under its retirement
     plan or wrap program. In addition, new accounts may be permitted in the
     Fund for certain plans and programs offered in connection with employer-
     sponsored retirement plans where the retirement plan has an existing
     account in the Fund. Requests for new accounts into a closed Fund will be
     reviewed by management on an individual basis, taking into consideration
     whether the addition to the Fund is believed to negatively impact existing
     Fund shareholders.

You should consider this information in deciding whether the Fund is an
appropriate investment for you.

                Please retain this Supplement with your records.