Exhibit No. 5.1


Cleary, Gottlieb, Steen & Hamilton
  One Liberty Plaza
  New York, NY 10006-1470
  (212) 225-2000
  Facsimile (212) 225-3999


                                        September 15, 2003

Standard Microsystems Corporation
80 Arkay Drive
Hauppauge, New York 11788

     Re:   Standard Microsystems Corporation Registration Statement on Form S-8

Ladies and Gentlemen:

     We have acted as counsel to Standard Microsystems  Corporation,  a Delaware
corporation (the "Company"), in connection with a registration statement on Form
S-8 (the  "Registration  Statement")  to be filed today with the  Securities and
Exchange  Commission (the "Commission")  pursuant to the Securities Act of 1933,
as  amended  (the  "Act"),  for the  registration  of  1,422,434  shares  of the
Company's  common  stock,  par value $0.10 per share (the  "Securities"),  to be
issued under the Company's  2003 Director  Stock Option Plan, the Company's 2003
Stock Option and Restricted  Stock Plan, the Company's  2002  Inducement  Option
Plan, and the Company's 2003 Inducement Option Plan (collectively, the "Plans"),
and the related Series A  Participating  Preferred  Stock  purchase  rights (the
"Rights") to be issued pursuant to the Rights Agreement (the "Rights Agreement")
dated as of January 7, 1998,  between  the  Company  and the Rights  Agent named
therein,  as amended by Amendment No. 1 dated  January 23, 2001,  and as further
amended by Amendment No. 2 dated April 9, 2002.

     We have  participated in the preparation of the Registration  Statement and
have reviewed the originals or copies  certified or otherwise  identified to our
satisfaction  of all such  corporate  records  of the  Company  and  such  other
instruments   and  other   certificates  of  public   officials,   officers  and
representatives  of the  Company and such other  persons,  and we have made such
investigations of law, as we have deemed appropriate as a basis for the opinions
expressed below.

     In rendering the opinions expressed below, we have assumed the authenticity
of  all  documents  submitted  to us as  originals  and  the  conformity  to the
originals  of all  documents  submitted to us as copies.  In  addition,  we have
assumed  and have not  verified  the  accuracy  as to  factual  matters  of each
document we have reviewed.

     Based  on the  foregoing,  and  subject  to  the  further  assumptions  and
qualifications set forth below, it is our opinion that:

          1. The Shares have been duly  authorized  by all  necessary  corporate
action of the  Company  and,  when  issued in  accordance  with the terms of the
Plans,  at prices in excess of the par value  thereof,  will be validly  issued,
fully paid and nonassessable.

          2. Upon  issuance  of the Shares in  accordance  with the terms of the
Plans, at prices in excess of the par value thereof,  the Rights associated with
the Shares will be validly issued.

          The foregoing  opinions are limited to the General  Corporation Law of
the State of Delaware.

          We hereby  consent to the filing of this  opinion as an exhibit to the
Registration  Statement. In giving such consent, we do not thereby admit that we
are "experts"  within the meaning of the Act or the rules and regulations of the
Commission  issued  thereunder  with  respect  to any  part of the  Registration
Statement, including this exhibit.
                  .

                                        Very truly yours,

                                        CLEARY, GOTTLIEB, STEEN & HAMILTON


                                        By:  /s/  Robert J. Raymond
                                        ----------------------------------------
                                             Robert J. Raymond, a partner