Exhibit 5         Opinion of Counsel




May 9, 2001

California Water Service Group
1720 North First Street
San Jose, CA 95112-4598

Ladies and Gentlemen:

    We have acted as counsel for  California  Water  Service  Group,  a Delaware
corporation  (the "Company"),  in connection with the Registration  Statement on
Form  S-8 to be  filed by the  Company  under  the  Securities  Act of 1933,  as
amended,  relating to the  registration of 1,500,000  shares of common stock, no
par  value  ("Shares")  which may be issued  from time to time  pursuant  to the
California Water Service Group Long Term Incentive Plan.

    We are of the opinion that the Shares have been duly authorized and that the
Shares,  when  issued  pursuant  to the  terms  described  in  the  Registration
Statement and in conformance with applicable state securities laws, will be duly
and validly issued, fully paid and nonassessable.

    We  hereby  consent  to the  filing  of this  opinion  as  Exhibit  5 to the
Registration  Statement  and to the use of our name  under  the  caption  "Legal
Matters" in the Registration Statement and in the Prospectus included therein.

                                               Very truly yours,

                                      McCUTCHEN, DOYLE, BROWN & ENERSEN, LLP

                                               by Thomas G. Reddy

                                              A Member of the Firm

                                       10