UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              Washington, D.C 20549


                                  SCHEDULE 13G


                    Under the Securities Exchange Act of 1934


                               (Amendment No. 1)*


                             A.O. SMITH CORPORATION
   _________________________________________________________________
                                (Name of Issuer)

                                 CLASS B COMMON
   _________________________________________________________________
                         (Title of Class of Securities)

                                    83186520
                       __________________________________
                                 (CUSIP Number)



   Check the following box  if a fee is being paid with  this statement /__/.
   (A fee  is not  required only  if the  filing person:  (1) has  a previous
   statement on file reporting beneficial ownership of more than five percent
   of the  class of  securities described  in Item  l; and (2)  has filed  no
   amendment  subsequent  thereto  reporting  beneficial  ownership  of  five
   percent or less of such class.) (See Rule 13d-7).

   *The remainder  of this cover  page shall  be filled out  for a  reporting
   person's initial filing on this form with respect to the  subject class of
   securities, and for any  subsequent amendment containing information which
   would alter the disclosures provided in a prior cover page.

   The information required in the remainder of this cover page  shall not be
   deemed  to be  "filed" for  the purpose  of Section  18 of  the Securities
   Exchange Act of 1934  ("Act") or otherwise subject  to the liabilities  of
   that section of  the Act but shall  be subject to all  other provisions of
   the Act (however, see the Notes).





   SEC 1745 (2/92)              Page 1 of 5 pages

   CUSIP No.    83186520               13G              Page  2  of  5  Pages

    1)  NAME OF REPORTING PERSON
        S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

                  Mitchell Hutchins Institutional Investors Inc.
                                 13-3180862

    2)  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                          (a) /__/
                                                          (b) /__/
    3)  SEC USE ONLY


    4)  CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

                       5)   SOLE VOTING POWER
    NUMBER OF
                                 -0-
     SHARES
                       6)   SHARED VOTING POWER
   BENEFICIALLY
                                 755,400
     OWNED BY
                       7)   SOLE DISPOSITIVE POWER
      EACH
                                 -0-
    REPORTING
                       8)   SHARED DISPOSITIVE POWER
     PERSON
                                 755,400
      WITH

    9)  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                                 755,400

   10)  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*


   11)  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

                                 5.20%

   12)  TYPE OF REPORTING PERSON*

                                 IA

                      *SEE INSTRUCTION BEFORE FILLING OUT!

                                                        Page  3  of  5  Pages

   Item 1.   (a)  Name of Issuer:

                  A.O. Smith Corporation

                  Address of Issuer's Principal Executive Offices:

                  11270 West Park Place
                  Milwaukee, WI  53224-3690


   Item 2.   (a)  Name of Person Filing:

                  Mitchell Hutchins Institutional Investors Inc.

             (b)  Address of Principal Business Office:

                  1285 Avenue of the Americas
                  New York, NY  10019

             (c)  Citizenship:                                       Delaware

             (d)  Title of Class of Securities:                Class B Common

             (e)  CUSIP Number:                                      83186520


   Item 3.   Type of Reporting Person

             (a)  (  ) Broker or  Dealer registered  under Section 15  of the
                       Act

             (b)  (  ) Bank as defined in Section 3(a)(6)of the Act

             (c)  (  ) Insurance Company  as defined  in Section  3(a)(19) of
                       the Act

             (d)  (  ) Investment Company  registered under Section 8  of the
                       Investment Company Act

             (e)  (XX) Investment Adviser Registered under Section 203 of the
                       Investment Advisers Act of 1940

                                                        Page  4  of  5  Pages

             (f)  (  ) Employee Benefit  Plan, Pension Fund which  is subject
                       to  the provisions  of the Employee  Retirement Income
                       Security Act  of 1974  or Endowment Fund;  see Section
                       240.13d-1(b)(1)(ii)(F)

             (g)  (  ) Parent  Holding Company,  in  accordance with  Section
                       240.13d-1(b)(ii)(G) (Note:  See Item 7)

             (h)  (  ) Group, in accordance with Section 240.13d-1
                       (b)(1)(ii)(H)

   Item 4.   Ownership:

             (a)  Amount Beneficially Owned:                          755,400

             (b)  Percent of Class:                                     5.20%

             (c)  Number of Shares as to which such person has:
                  (i)   Sole Power to vote or to direct 
                        the vote:                                         -0-

                  (ii)  Shared Power to vote or to direct
                        the vote:                                     755,400

                  (iii) Sole Power to dispose or to direct
                        the disposition of:                               -0-

                  (iv)  Shared Power to dispose or to
                        direct the disposition of:                    755,400

   Item 5. Ownership of Five Percent or Less of a Class:

           N/A

   Item 6. Ownership of More than Five Percent on Behalf of Another:

           N/A

                                                        Page  5  of  5  Pages

   Item 7.   Identification  and  Classification  of  the   Subsidiary  Which
             Acquired the Security  Being Reported on  by the Parent  Holding
             Company:

             N/A

   Item 8.   Identification and Classification of Members of the Group:

             N/A

   Item 9.   Notice of Dissolution of Group:

             N/A

   Item 10.  Certification:

             By signing below I certify that, to the best of my knowledge and
             belief, the  securities referred to  above were acquired  in the
             ordinary  course  of business  and  were  not acquired  for  the
             purpose of and do not have the effect of changing or influencing
             the  control of  the  issuer of  such  securities and  were  not
             acquired   in  connection  with  or  as  a  participant  in  any
             transaction having such purposes or effect.

             Signature:

             After reasonable inquiry  and to  the best of  my knowledge  and
             belief,  I  certify  that  the information  set  forth  in  this
             statement is true, complete and correct.

                  /s/ William R. Cavell
             By: ____________________________
                  William R. Cavell
                  Legal Department

             Date:  February 7, 1994