Exhibit 99.1350CERT

         Certification Pursuant to Rule 30a-2(b) under the 1940 Act and
                      Section 906 of the Sarbanes Oxley Act

Pursuant to 18 U.S.C. ss. 1350, the undersigned officer of BlackRock California
Insured Municipal Bond Fund of BlackRock California Municipal Series Trust (the
"Registrant"), hereby certifies, to the best of his knowledge, that the
Registrant's Report on Form N-CSR for the period ended August 31, 2007, (the
"Report") fully complies with the requirements of Section 15(d) of the
Securities Exchange Act of 1934, as amended, and that the information contained
in the Report fairly presents, in all material respects, the financial condition
and results of operations of the Registrant.

Date: October 22, 2007


/s/ Robert C. Doll, Jr.
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Robert C. Doll, Jr.,
Chief Executive Officer (principal executive officer) of
BlackRock California Insured Municipal Bond Fund of
BlackRock California Municipal Series Trust

Pursuant to 18 U.S.C. ss. 1350, the undersigned officer of BlackRock California
Insured Municipal Bond Fund of BlackRock California Municipal Series Trust (the
"Registrant"), hereby certifies, to the best of his knowledge, that the
Registrant's Report on Form N-CSR for the period ended August 31, 2007, (the
"Report") fully complies with the requirements of Section 15(d) of the
Securities Exchange Act of 1934, as amended, and that the information contained
in the Report fairly presents, in all material respects, the financial condition
and results of operations of the Registrant.

Date: October 22, 2007


/s/ Donald C. Burke
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Donald C. Burke,
Chief Financial Officer (principal financial officer) of
BlackRock California Insured Municipal Bond Fund of
BlackRock California Municipal Series Trust

This certification is being furnished pursuant to Rule 30a-2(b) under the
Investment Company Act of 1940, as amended, and 18 U.S.C. Section 1350 and is
not being filed as part of the Form N-CSR with the Securities and Exchange
Commission.