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                                                                                                May 10, 2007

Dr. Leonard S. Schleifer, M.D., Ph.D
President and Chief Executive Officer
Regeneron Pharmaceuticals, Inc.
777 Old Saw Mill River Road
Tarrytown, New York 10591-6707

Re:      Regeneron Pharmaceuticals, Inc.
Form 10-K for fiscal year ended December 31, 2006
            File No. 000-19034

Dear Dr. Schleifer:

We have reviewed your filing and have the following comments. We have limited
our review to only your financia l statements and related disclosures and do not intend to
expand our review to other portions of your documents. In our comments, we ask you to
provide us with information so we may better understand your disclosure.  After
reviewing this information, we may raise additional comments.

 Please understand that the purpose of our re view process is to assist you in your
compliance with the applicable disclosure requirements and to enhance the overall disclosure in your filing.  We look forward to  working with you in these respects.  We
welcome any questions you may have about our comments or any other aspect of our review.  Feel free to call us at the telephone numbers listed at the end of this letter.

Form 10-K for fiscal year  ended December 31, 2006

Managements Discussion and Analysis of Fi nancial Condition and Re sults of Operations

Research and Development Expenses, page 36
1. We believe your disclosure related to re search and development expenses could
be improved by separately quantifying co sts incurred for your product candidates,
principally VGEF Trap-Oncology, VEGF Tr ap-Eye and IL-1 Trap and provide
information that would allow investors to determine the reasonably likely timing for commercialization of your lead drug candidates and related revenue
generation. Please provide in disclosure-t ype format the following information for
each of your major research and developm ent projects. Refer to the Division of

Dr. Leonard S. Schleifer, M.D., Ph.D
Regeneron Pharmaceuticals, Inc.
May 10, 2007 Page 2
Corporation Finance “Current Issues a nd Rulemaking Projects Quarterly Update”
under section VIII – Industry Specific Issues – Accounting and Disclosure by
Companies Engaged in Research and Deve lopment Activities.  You can find it at
the following website address:
http://www.sec.gov/divisions/c orpfin/cfcrq032001.htm#secviii .

a. The costs incurred during each period presented and to date on the project;
b. The nature, timing and estimated costs of the efforts necessary to complete the project;
c. The anticipated completion date for the project;
d. The risks and uncertainties associated with completing development on schedule, and the consequences to oper ations, financial position and liquidity
if the project is not completed timely; and,
e. The period in which material net cash in flows from the project are expected
to commence.

Regarding “a,” if you do not maintain any research and development costs by project, explain why management does not maintain and evaluate research and development costs by project.  Provide othe r quantitative or qualitative disclosure
that indicates the amount of the compa ny’s resources being used on the project.

Regarding “b” and “c,” provide the amount or range of estimated costs and timing
to complete the phase in process and each future phase. To the extent that
information is not estimable, describe t hose facts and circumstances indicating the
uncertainties that preclude you fr om making a reasonable estimate.

Funding Requirements, page 44
2. Please explain in disclosure-type format your basis for omitting estimated payments from the table of contractual oblig ations that appear reasonably likely to
arise from your research and development agreements with sanofi-aventis and Bayer Healthcare LLC. Discuss how profitabi lity will be measured, your expected
timing for achieving profitability and payment of development expense reimbursements if the collabo rations are profitable.

Critical Accounting Policies and Si gnificant Judgments and Estimates

Revenue Recognition, page 46

3. You do not appear to have discussed the va riability implicit in critical accounting
estimates associated with your revenue recognition of contra ct research and
development and research progress payments. Your disclosure should provide investors with a fuller unde rstanding of the uncertain ties in applying critical
accounting estimates and the likelihood th at materially different amounts would

Dr. Leonard S. Schleifer, M.D., Ph.D
Regeneron Pharmaceuticals, Inc.
May 10, 2007 Page 3
be reported under different conditions or using different assu mptions. It should
include quantification of the related variab ility in operating results that you expect
to be reasonably likely to occur. Please  describe in disclosure-type format the
expected uncertainties and variability im plicit in critical accounting estimates
associated with your revenue recogniti on of these payments, the effect that
changes in such estimates have had on your financial statements for each period presented, and the effect that reasonabl y likely changes in the key assumptions
underlying these estimates may have on your financial statements in the future. Also, explain your basis for concluding th at research and development activities
other than clinical trial expenses do not  involve critical ac counting estimates.

4. You record substantive performance m ilestones in accordance with various
criteria, including whether a “reasonab le amount of time has passed between
receipt of an upfront payment and achie vement of the milestone and the amount
of the milestone is reasonable in relation to the effort, value and risk associated
with achieving the milestone.” Please explain in disclosure-type format the factors that you consider in evaluating these tw o revenue recognition criteria, including
the quantifications associated with the term, “reasonable.”

Clinical Trial Accrual Estimates, page 46

5. You expense certain clinical trial costs “b ased on the total number of patients in
the trial, the rate at which patients enter the trial and the period over which clinical investigators or c ontract research organizations  are expected to provide
services.”  Please provide in disclosure -type format the signi ficant terms of your
arrangements with clinical investigators and contract rese arch organizations,
including payment schedules.  Include in  your discussion an explanation of the
methods and key assumptions used for accruing and recognizi ng clinical trial
costs.
*    *    *    *

Please respond to these comments within  10 business days or tell us when you
will provide us with a respons e.  Your letter should key your responses to our comments.
Detailed cover letters greatly facilitate our review.  Please furnish your letter on EDGAR
under the form type label CORRESP.

We urge all persons who are responsible for the accuracy and adequacy of the
disclosure in the filing to be certain that the filing includes all in formation required under
the Securities Exchange Act of 1934 and th at they have provided all information
investors require for an informed invest ment decision.  Since the company and its
management are in possession of all facts re lating to a company’s disclosure, they are
responsible for the accuracy and adequacy of the disclosures they have made.

Dr. Leonard S. Schleifer, M.D., Ph.D
Regeneron Pharmaceuticals, Inc.
May 10, 2007 Page 4
 In connection with responding to our co mments, please provide, in your letter, a
statement from the company acknowledging that:

• the company is responsible for the adequacy  and accuracy of the disclosure in the
filings;
• staff comments or changes to disclosure  in response to staff comments do not
foreclose the Commission from taking any action with respect to the filing; and
• the company may not assert staff comme nts as a defense in any proceeding
initiated by the Commission or any person under the federal secu rities laws of the
United States.

 In addition, please be advi sed that the Division of En forcement has access to all
information you provide to the staff of the Divi sion of Corporation Fi nance in our review
of your filing or in response to our comments on your filing.

You may contact Frank Wyman, St aff Accountant, at 202-551-3660  or Don
Abbott, Senior Staff Accountant, at 202- 551-3608, if you have questions regarding the
comments.  In this regard, do not hes itate to contact me, at (202) 551-3679.

       S i n c e r e l y ,

       J i m  B .  R o s e n b e r g
      Senior Assistant Chief Accountant