Morgan, Lewis & Bockius LLP                                           Exhibit 11
1111 Pennsylvania Avenue, NW
Washington, DC  20004

March 27, 2009

Rydex Series Funds
9601 Blackwell Road
Suite 500
Rockville, MD 20850

Re:  Opinion of Counsel regarding the Registration Statement/Proxy Statement
     filed on Form N-14 under the Securities Act of 1933

Ladies and Gentlemen:

We have acted as counsel to Rydex Series Funds, a Delaware statutory trust (the
"Trust"), in connection with the above-referenced registration statement/proxy
statement on Form N-14 (the "Registration Statement"), which relates to the
Trust's Investor2 Class shares of beneficial interest, without par value
(collectively, the "Shares") of the U.S. Government Money Market Fund (the
"Fund") to be issued in connection with the reorganization of the Security Cash
Fund into the Fund. This opinion is being delivered to you in connection with
the Trust's filing of the Registration Statement with the U.S. Securities and
Exchange Commission (the "SEC") pursuant to Rule 488(a) under the Securities Act
of 1933, as amended (the "1933 Act"). With your permission, all assumptions and
statements of reliance herein have been made without any independent
investigation or verification on our part except to the extent otherwise
expressly stated, and we express no opinion with respect to the subject matter
or accuracy of such assumptions or items relied upon.

In connection with this opinion, we have reviewed, among other things, executed
copies of the following documents:

     (a)  a certificate of the State of Delaware as to the existence and good
          standing of the Trust;

     (b)  copies of the Trust's Declaration of Trust and all amendments and
          supplements thereto (the "Declaration of Trust");

     (c)  a certificate executed by Joanna M. Haigney, Secretary of the Trust,
          certifying, and attaching copies of, the Trust's Declaration of Trust
          and By-Laws (the "By-Laws"), and certain resolutions adopted by the
          Board of Trustees of the Trust authorizing the issuance of the Shares
          of the Fund; and

     (d)  a printer's proof of the Registration Statement.


In our capacity as counsel to the Trust, we have examined the originals or
certified, conformed or reproduced copies of all records, agreements,
instruments and documents as we have deemed relevant or necessary as the basis
for the opinion hereinafter expressed. In all such examinations, we have assumed
the legal capacity of all natural persons executing documents, the genuineness
of all signatures, the authenticity of all original or certified copies, and the
conformity to original or certified copies of all copies submitted to us as
conformed or reproduced copies. As to various questions of fact relevant to such
opinion, we have relied upon, and assume the accuracy of, certificates and oral
or written statements of public officials and officers or representatives of the
Trust. We have assumed that the Registration Statement, as filed with the SEC,
will be in substantially the form of the printer's proof referred to in
paragraph (d) above.

Based upon, and subject to, the limitations set forth herein, we are of the
opinion that the Shares, when issued and sold in accordance with the Declaration
of Trust and By-Laws, and for the consideration described in the Registration
Statement, will be legally issued, fully paid and non-assessable under the laws
of the State of Delaware.

We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. In giving this consent, we do not concede that we are in
the category of persons whose consent is required under Section 7 of the 1933
Act.

Very truly yours,

/s/ Morgan, Lewis & Bockius LLP
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