Washington, D.C. 20549


Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
OMB Number: 3235-0104
Estimated average burden
hours per response: 0.5
1. Name and Address of Reporting Person*
Sherif Tarek

(Last) (First) (Middle)


(City) (State) (Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
3. Issuer Name and Ticker or Trading Symbol
Medidata Solutions, Inc. [ MDSO ]
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director 10% Owner
X Officer (give title below) Other (specify below)
Chairman & CEO
5. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
X Form filed by One Reporting Person
Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock 1,428,806 D
Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4) 2. Date Exercisable and Expiration Date (Month/Day/Year) 3. Title and Amount of Securities Underlying Derivative Security (Instr. 4) 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 6. Nature of Indirect Beneficial Ownership (Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Option (right to buy) (1) 08/13/2018 Common Stock 36,730 19.75 D
Explanation of Responses:
1. 1/48th of these options vest and become exercisable each month over four years, commencing on August 13, 2008, the date of grant. Of these options, options to purchase 29,079 shares remain unvested.
Exhibit List - Exhibit 24-Limited Power of Attorney for Section 16(a) Reporting.
/s/ Michael I. Otner, Attorney-in-Fact 06/24/2009
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
                                POWER OF ATTORNEY

        Know all by  these  presents,  that the  undersigned,  as a  Section  16
reporting person of Medidata Solutions, Inc. (the "Company"), hereby constitutes
and appoints each of Bruce D. Dalziel and Michael I. Otner,  signing singly, the
undersigned's true and lawful attorney-in-fact to:

        (1) prepare,  execute in the undersigned's name and on the undersigned's
        behalf, and submit to the U.S.  Securities and Exchange  Commission (the
        "SEC") a Form ID, including  amendments thereto, and any other documents
        necessary  or  appropriate  to obtain codes and  passwords  enabling the
        undersigned to make electronic  filings with the SEC of reports required
        by Section 16(a) of the  Securities  Exchange Act of 1934 or any rule or
        regulation of the SEC;

        (2)  execute  for and on behalf  of the  undersigned,  as a  Section  16
        reporting  person of the Company,  Forms 3, 4, and 5 in accordance  with
        Section  16(a) of the  Securities  Exchange  Act of 1934  and the  rules
        thereunder,  and any  other  forms or  reports  the  undersigned  may be
        required  to  file  in  connection  with  the  undersigned's  ownership,
        acquisition, or disposition of securities of the Company;

        (3) do and perform any and all acts for and on behalf of the undersigned
        which may be  necessary
  or  desirable  to complete and execute any such
        Form 3, 4, or 5, or other form or report,  and timely  file such form or
        report with the SEC and any stock exchange or similar authority; and

        (4) take any other action of any type  whatsoever in connection with the
        foregoing  which,  in the  opinion of such  attorney-in-fact,  may be of
        benefit  to,  in the best  interest  of, or  legally  required  by,  the
        undersigned,  it being  understood  that the documents  executed by such
        attorney-in-fact on behalf of the undersigned  pursuant to this Power of
        Attorney  shall  be in such  form  and  shall  contain  such  terms  and
        conditions    as   such    attorney-in-fact    may   approve   in   such
        attorney-in-fact's discretion.

        The undersigned hereby grants to each such  attorney-in-fact  full power
and  authority  to do and  perform  any  and  every  act  and  thing  whatsoever
requisite,  necessary, or proper to be done in the exercise of any of the rights
and  powers  herein  granted,  as  fully  to all  intents  and  purposes  as the
undersigned  might  or  could  do if  personally  present,  with  full  power of
substitution  or  revocation,  hereby  ratifying  and  confirming  all that such
attorney-in-fact,  or such attorney-in-fact's  substitute or substitutes,  shall
lawfully  do or cause to be done by virtue  of this  Power of  Attorney  and the
rights  and  powers  herein  granted.  The  undersigned  acknowledges  that  the
foregoing  attorneys-in-fact,  in serving in such capacity at the request of the
undersigned,  are  not  assuming,  nor  is  the  Company  assuming,  any  of the
undersigned's  responsibilities  to comply  with  Section  16 of the  Securities
Exchange Act of 1934.

        This Power of Attorney  shall  remain in full force and effect until the
undersigned is no longer  required to file Forms 3, 4, and 5 with respect to the
undersigned's  holdings of and transactions in securities issued by the Company,
unless earlier revoked by the  undersigned in a signed writing  delivered to the
foregoing attorneys-in-fact.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 8th day of June, 2009.

                             Signature: /s/ TAREK SHERIF

                            Print Name: Tarek Sherif