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dateYear2007Day27Month7lstransJuly 27, 2007

Securities and Exchange Commission
Streetaddress100 F Street, N.E.
CityplaceWashington, StateDC PostalCode20549

Commissioners:

We have read the statements made by MFS California  Insured  Municipal Fund (the
"Fund",  formerly known as Colonial  California  Insured  Municipal  Fund) (copy
attached),  which we understand  will be filed with the  Securities and Exchange
Commission, pursuant to Item 77K of Form N-SAR, as part of the Fund's Form N-SAR
report for the period ended dateYear2007Day31Month5lstransMay 31, 2007. We agree
with the statements concerning our Firm in such Form N-SAR.

Very truly yours,



PricewaterhouseCoopers LLP





On  dateYear2007Day29Month6lstransJune   29,  2007,  PricewaterhouseCoopers  LLP
("PwC") resigned as the independent  registered  public  accounting firm for the
Trust. During the two most recent fiscal years, PwC's audit reports contained no
adverse  opinion or  disclaimer  of opinion;  nor were its reports  qualified or
modified as to uncertainty,  audit scope, or accounting principles.  Further, in
connection  with its audits for the two most  recent  fiscal  years and  through
dateYear2007Day29Month6lstransJune 29, 2007, there were no disagreements between
the Trust and PwC on any matter of accounting principles or practices, financial
statement  disclosure or auditing scope or procedure,  which, if not resolved to
the  satisfaction  of PwC, would have caused it to make reference to the subject
matter of the  disagreement  in its report on the financial  statements for such
years. Effective  dateYear2007Day29Month6lstransJune 29, 2007, Ernst & Young LLP
was appointed by the audit committee of the Board of Trustees as the independent
registered  public  accounting  firm of the  Trust  for the  fiscal  year  ended
dateYear2007Day30Month11lstransNovember 30, 2007.