SECURITIES AND EXCHANGE COMMISSION
                               WASHINGTON, D.C. 20549
                                     FORM 10-K/A
                                  (Amendment No. 2)

(MARK ONE)
     
     /X/  Annual report pursuant to section 13 or 15(d) of the Securities
          Exchange Act of 1934 for the fiscal year ended October 4, 1998.
     / /  Transition report pursuant to section 13 or 15(d) of the Securities
          Exchange Act of 1934 for the transition period from __________
          to__________.

     Commission file number 0-19655

                                   TETRA TECH, INC.
                (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

     
             Delaware                                95-4148514
  (State or other jurisdiction of         (I.R.S. Employer Identification No.)
   incorporation or organization)


            670 N. Rosemead Blvd.
             Pasadena, California                                  91107
(Address of registrant's principal executive offices)            (Zip Code)


(Registrant's telephone number, including area code:)           (626) 351-4664


Securities registered pursuant to Section 12(b) of the Act:      
     
(Title of each class)              (Name of each exchange on which registered)

     None                                                   None


Securities registered pursuant to Section 12(g) of the Act: 
          
                                   (Title of Class)
                             Common Stock, $.01 par value


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.  Yes /X/   No / / 

The aggregate market value of the voting stock held by non-affiliates of the
registrant on December 18, 1998 was $577,495,874.

The number of shares of Common Stock, $.01 par value, outstanding (the only
class of common stock of the registrant outstanding) was 28,666,131 on December
18, 1998.

Portions of registrant's Annual Report to Stockholders for the fiscal year ended
October 4, 1998 are incorporated by reference in Part II of this report. 
Portions of registrant's Proxy Statement for our 1999 Annual Meeting of
Stockholders are incorporated by reference in Part III of this report.

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. / /



       The undersigned Registrant hereby amends Exhibit 21 of its Annual 
Report on Form 10-K for the fiscal year ended October 4, 1998, by replacing 
it with the attached exhibit.





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                                    SIGNATURES    


     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.



                                   TETRA TECH, INC.    


     Date:  March 4, 1999       By: /s/ Li-San Hwang
                                       ----------------------------------------
                                       Li-San Hwang, Chairman of the Board of
                                       Directors, President and Chief Executive
                                       Officer 


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