N-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-Q

QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF

REGISTERED MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811-9537

MFS CALIFORNIA INSURED MUNICIPAL FUND

(Exact name of registrant as specified in charter)

500 Boylston Street, Boston, Massachusetts 02116

(Address of principal executive offices) (Zip code)

Susan S. Newton

Massachusetts Financial Services Company

500 Boylston Street

Boston, Massachusetts 02116

(Name and address of agents for service)

Registrant’s telephone number, including area code: (617) 954-5000

Date of fiscal year end: November 30

Date of reporting period: August 31, 2008

ITEM 1. SCHEDULE OF INVESTMENTS.

MFS California Insured Municipal Fund

PORTFOLIO OF INVESTMENTS (Unaudited) 8/31/08

Issuer	Shares/Par		Value ($)
Municipal Bonds – 169.2%
Airport & Port Revenue – 5.8%
Port of Oakland, CA, “A”, MBIA, 5%, 2026	$	500,000	$	458,690
Port of Oakland, CA, “K”, FGIC, 5.75%, 2029		1,000,000		995,070
San Diego County, CA, Regional Airport Authority, AMBAC, 5.25%, 2020		500,000		511,110
			$	1,964,870
General Obligations - General Purpose – 6.4%
State of California, AMBAC, 6%, 2017	$	1,000,000	$	1,158,598
State of California, AMBAC, 5%, 2034		1,000,000		1,006,160
			$	2,164,758
General Obligations - Schools – 19.8%
Culver City, CA, School Facilities Financing Authority Rev. (Culver City Unified School District), FSA, 5.5%, 2025	$	1,000,000	$	1,109,920
Dublin, CA, Unified School District (Election of 2004), “C”, MBIA, 0%, 2032		3,000,000		762,870
Pomona, CA, Unified School District, “A”, MBIA, 6.55%, 2029		1,000,000		1,119,520
Rescue, CA, Unified School District (Election of 1998), MBIA, 0%, 2026		1,125,000		435,893
Union, CA, Elementary School District, “A”, FGIC, 0%, 2018		1,630,000		1,041,863
Vallejo City, CA, Unified School District, “A”, MBIA, 5.9%, 2025		500,000		503,450
West Contra Costa, CA, Unified School District, “A”, MBIA, 5.7%, 2023		500,000		532,180
West Covina, CA, Unified School District, “A”, MBIA, 5.8%, 2021		500,000		542,650
Yuba City, CA, Unified School District, FGIC, 0%, 2018		1,000,000		636,060
			$	6,684,406
Healthcare Revenue - Hospitals – 15.5%
ABAG Finance Authority Rev. (Jackson Lab), 5.75%, 2037	$	385,000	$	387,318
California Municipal Finance Authority, Certificates of Participation (Community Hospitals of Central California), 5.25%, 2027		250,000		227,963
California Statewide Communities Development Authority Rev. (Adventist), ASSD GTY, 5%, 2037		405,000		392,445
California Statewide Communities Development Authority Rev. (Catholic Healthcare West) “K”, ASSD GTY, 5.5%, 2041		1,000,000		1,019,520
California Statewide Communities Development Authority Rev. (Catholic West), 6.5%, 2010 (c)		145,000		157,885
California Statewide Communities Development Authority Rev. (Daughters of Charity Health), “A”, 5.25%, 2030		500,000		453,530
California Statewide Communities Development Authority Rev. (Kaiser Permanente), “B”, BHAC, 5%, 2041		540,000		534,006
California Statewide Communities Development Authority Rev. (St. Joseph Health System), FGIC, 5.75%, 2047		500,000		514,315
Oakland, CA, Rev. (Harrison Foundation), “A”, AMBAC, 6%, 2010 (c)		1,000,000		1,054,850
Santa Clara County, CA, Financing Authority Rev. (El Camino Hospital), AMBAC, 5.125%, 2041		400,000		382,056
Sierra View, CA, Local Health Care District Rev., 5.25%, 2037		130,000		116,479
			$	5,240,367
Healthcare Revenue - Long Term Care – 6.8%
ABAG Finance Authority for Non-Profit Corps. (Odd Fellows Home), MBIA, 6%, 2024	$	2,000,000	$	2,013,380
California Statewide Communities Development Authority Rev. (Eskaton Properties, Inc.), 8.25%, 2010 (c)		250,000		282,875
			$	2,296,255
Human Services – 0.4%
California Statewide Communities Development Authority Rev. (Inland Regional Center), 5.375%, 2037	$	140,000	$	126,923
Industrial Revenue - Other – 1.2%
California Statewide Communities Development Authority Rev. (Anheuser-Busch), 4.8%, 2046	$	500,000	$	393,360

1

MFS California Insured Municipal Fund

PORTFOLIO OF INVESTMENTS (Unaudited) 8/31/08 - continued

Issuer	Shares/Par		Value ($)
Municipal Bonds – continued
Miscellaneous Revenue - Other – 3.4%
California Infrastructure & Economic Development Bank Rev. (Walt Disney Family Museum), 5.25%, 2033	$	160,000	$	160,462
San Francisco, CA, City & County Redevelopment Agency, Hotel Tax Rev., FSA, 6.75%, 2025		1,000,000		1,002,730
			$	1,163,192
Single Family Housing - Local – 2.7%
California Housing Finance Agency Rev., “A”, 4.95%, 2036	$	1,000,000	$	863,950
California Rural Home Mortgage Finance Authority Rev., Mortgage Backed Securities Program, “A”, GNMA, 6.35%, 2029		20,000		20,273
California Rural Home Mortgage Finance Authority Rev., Mortgage Backed Securities Program, “B4”, GNMA, 6.35%, 2029		20,000		20,035
			$	904,258
Single Family Housing - Other – 2.6%
California Department of Veterans Affairs, Home Purchase Rev., “B”, 5.25%, 2037	$	1,000,000	$	893,170
Single Family Housing - State – 2.7%
California Housing Finance Agency Rev., Home Mortgage, “E”, FGIC, 5.05%, 2026	$	995,000	$	919,997
Solid Waste Revenue – 1.4%
Salinas Valley, CA, Solid Waste Authority Rev., AMBAC, 5.125%, 2022	$	500,000	$	493,375
State & Local Agencies – 31.6%
Calabasas, CA, Certificate Participants (City Hall & Civic Center Project),, AMBAC, 4.5%, 2041	$	725,000	$	634,259
Golden State, CA, Tobacco Securitization Corp., Tobacco Settlement Rev., SBHAC, 5%, 2038		1,000,000		1,004,470
Golden State, CA, Tobacco Securitization Corp., Tobacco Settlement Rev., Enhanced, “A”, FGIC, 5%, 2035		1,000,000		918,540
Golden State, CA, Tobacco Securitization Corp., Tobacco Settlement Rev., Enhanced, “A”, FGIC, 5%, 2038		1,000,000		911,600
Huntington Park, CA, Public Financing Authority Rev., “A”, FSA, 5.25%, 2019		1,000,000		1,082,340
Los Angeles County, CA, Schools Regionalized Business Service Corp., Capital Appreciation Pooled Financing, “A”, AMBAC, 0%, 2018		2,020,000		1,289,709
Los Angeles County, CA, Schools Regionalized Business Service Corp., Capital Appreciation Pooled Financing, “A”, AMBAC, 0%, 2023		2,220,000		1,029,703
Pacifica, CA, Certificates of Participation (Street Improvement Project), AMBAC, 5.875%, 2009 (c)		1,500,000		1,601,445
Sacramento, CA, City Financing Authority (Master Lease Program Facilities), “E”, AMBAC, 5.25%, 2026		1,000,000		1,065,530
Western Placer, CA, Unified School, “B”, ASSD GTY, 5.125%, 2047		1,200,000		1,142,784
			$	10,680,380
Tax - Other – 2.2%
Southern California Logistics Airport Authority (Southern California Authority Project), XLCA, 5%, 2043	$	820,000	$	754,023
Tax Assessment – 16.2%
Compton, CA, Public Finance Authority, AMBAC, 5%, 2032	$	500,000	$	477,805
Fontana, CA, Public Finance Authority, Tax Allocation Rev. (Sub Lien North Fontana Redevelopment), “A”, AMBAC, 5%, 2029		1,000,000		988,410
Huntington Beach, CA, Community Facilities District, Special Tax (Grand Coast Resort), “2000-1”, 6.45%, 2031		100,000		101,572
Lancaster, CA, Financing Authority, Tax Allocation Rev. (Projects No. 5 & 6 Redevelopment Projects), MBIA, 5.25%, 2020		1,075,000		1,164,257
Long Beach, CA, Bond Finance Authority, Tax Allocation Rev., “C”, AMBAC, 5.5%, 2031		750,000		768,870
Oceanside, CA, Community Development Commission, Tax Allocation (Downtown Redevelopment Project Escrow Bonds), 5.7%, 2025		500,000		503,445

2

MFS California Insured Municipal Fund

PORTFOLIO OF INVESTMENTS (Unaudited) 8/31/08 - continued

Issuer	Shares/Par		Value ($)
Municipal Bonds – continued
Tax Assessment – continued
Orange County, CA, Community Facilities District, Special Tax (Ladera Ranch), “A”, 6.7%, 2009 (c)	$	200,000	$	213,628
San Dieguito, CA, Public Facilities Authority, “A”, AMBAC, 5%, 2032		500,000		481,090
San Jose, CA, Redevelopment Agency, Tax Allocation (Merged Area Redevelopment Project), “C”, MBIA, 4.25%, 2030		900,000		767,223
			$	5,466,300
Tobacco – 5.8%
Golden State, CA, Tobacco Securitization Corp., Tobacco Settlement Rev., “A-1”, 5.75%, 2047	$	1,500,000	$	1,233,915
Golden State, CA, Tobacco Securitization Corp., Tobacco Settlement Rev., Asset Backed, “A-1”, 5.125%, 2047		1,000,000		740,660
			$	1,974,575
Transportation – Special Tax – 5.5%
Puerto Rico Highway & Transportation Authority, Highway Rev., “Y”, FSA, 5.5%, 2016 (c)	$	1,000,000	$	1,157,300
San Francisco, CA, Bay Area Rapid Transit District, Sales Tax Rev., “A”, MBIA, 5%, 2030 (f)		685,000		695,234
			$	1,852,534
Universities – Colleges – 14.6%
Allan Hancock, CA, Joint Community College (Election of 2006), “A”, FSA, 4.375%, 2031	$	100,000	$	91,656
California Educational Facilities Authority Rev. (Pepperdine University), “A”, AMBAC, 5%, 2035		1,000,000		1,001,130
California Educational Facilities Authority Rev., “B”, 6.625%, 2010 (c)		205,000		223,009
California Educational Facilities Authority Rev., “B”, 6.625%, 2010 (c)		45,000		48,953
California University Rev., “C”, MBIA, 5%, 2029		1,500,000		1,509,765
Chabot Las Positas, CA, Community College (Election of 2004), “B”, AMBAC, 0%, 2026		970,000		370,957
Hastings College of the Law, CA, ASSD GTY, 4.75%, 2037		195,000		183,113
Rancho Santiago, CA, Community College District, FSA, 5.125%, 2029		1,000,000		1,078,630
University Enterprises, Inc. (Auxiliary Organization), “A”, FGIC, 4.375%, 2030		500,000		419,325
			$	4,926,538
Utilities – Investor Owned – 9.0%
California Pollution Control Financing Authority, Pollution Control Rev. (Pacific Gas & Electric Co.), MBIA, 5.35%, 2016	$	1,000,000	$	1,033,090
California Pollution Control Financing Authority, Pollution Control Rev. (San Diego Gas & Electric Co.), “A”, 6.8%, 2015		500,000		561,865
California Pollution Control Financing Authority, Pollution Control Rev. (Southern California Edison Co.), “B”, MBIA, 5.45%, 2029		1,500,000		1,447,305
			$	3,042,260
Utilities – Other – 1.6%
Southern California Public Power Authority (Natural Gas Project No. 1), “A”, 5%, 2033	$	585,000	$	548,379
Water & Sewer Utility Revenue – 14.0%
Culver City, CA, Wastewater Facilities Rev., “A”, FGIC, 5.7%, 2029	$	1,500,000	$	1,555,485
Los Angeles, CA, Department of Water & Power, Waterworks Rev., “C”, MBIA, 5%, 2022		1,000,000		1,035,150
Pico Rivera, CA, Water Authority Rev. (Water Systems Project), “A”, MBIA, 5.5%, 2029		2,000,000		2,137,480
			$	4,728,115
Total Municipal Bonds			$	57,218,035
Floating Rate Demand Notes – 5.0%
East Baton Rouge, LA, Pollution Control Rev. (Exxon Mobil Corp.), 2%, due 9/02/08	$	100,000	$	100,000
Jacksonville, FL, Pollution Control Rev. (Florida Power & Light Co.), 2.29%, due 9/02/08		300,000		300,000

3

MFS California Insured Municipal Fund

PORTFOLIO OF INVESTMENTS (Unaudited) 8/31/08 - continued

Issuer	Shares/Par		Value ($)
Floating Rate Demand Notes – continued
Lincoln County, WY, Pollution Control Rev. (Exxon Mobil Corp.), “B”, 2.2%, due 9/02/08	$	800,000	$	800,000
Mt. Vernon Industrial Pollution Control Rev. (General Electric Co.), 2.27%, due 9/02/08		100,000		100,000
Sublette County, WY, Pollution Control Rev. (Exxon Mobil Corp.), 2%, due 9/02/08		400,000		400,000
Total Floating Rate Demand Notes			$	1,700,000
Total Investments			$	58,918,035
Other Assets, Less Liabilities – (1.9)%				(641,581	)
Preferred shares (Issued by the Fund) – (72.3)%				(24,450,000	)
Net Assets applicable to common shares – 100.0%			$	33,826,454

(c) Refunded bond.

(f) All or a portion of the security has been segregated as collateral for open futures contracts.

The following abbreviations are used in this report and are defined:

SIFMA Securities Industry and Financial Markets Association.

Insurers
AMBAC	AMBAC Indemnity Corp.
ASSD GTY	Assured Guaranty Insurance Co.
BHAC	Berkshire Hathaway Assurance Corp.
FGIC	Financial Guaranty Insurance Co.
FSA	Financial Security Assurance Inc.
GNMA	Government National Mortgage Assn.
MBIA	MBIA Insurance Corp.
SBHAC	Secondary Berkshire Hathaway Assurance Corp.
XLCA	XL Capital Insurance Co.

See attached supplemental information. For more information see notes to financial statements as disclosed in the most recent semiannual or annual report.

4

MFS California Insured Municipal Fund

Supplemental Information (Unaudited) 8/31/08

(1) Fair Value Disclosure

The fund adopted FASB Statement No. 157, Fair Value Measurements (the “Statement”) in this reporting period. This Statement provides a single definition of fair value, a hierarchy for measuring fair value and expanded disclosures about fair value measurements.

Various inputs are used in determining the value of the fund’s assets or liabilities carried at market value. These inputs are categorized into three broad levels. Level 1 includes quoted prices in active markets for identical assets or liabilities. Level 2 includes other significant observable market-based inputs (including quoted prices for similar securities, interest rates, prepayment speed, and credit risk). Level 3 includes unobservable inputs, which may include the adviser’s own assumptions in determining the fair value of investments. Other financial instruments are derivative instruments not reflected in total investments, such as futures, forwards, swap contracts and written options, which are valued at the unrealized appreciation/depreciation on the instrument. The following is a summary of the levels used as of August 31, 2008 in valuing the fund’s assets or liabilities carried at market value:

	Level 1		Level 2			Level 3		Total
Investments in Securities	$	—	$	58,918,035		$	—	$	58,918,035
Other Financial Instruments	$	1,471	$	(215,570	)	$	—	$	(214,099	)

(2) Portfolio Securities

The cost and unrealized appreciation and depreciation in the value of the investments owned by the fund, as computed on a federal income tax basis, are as follows:

Aggregate Cost	$	59,015,764
Gross unrealized appreciation	$	1,728,211
Gross unrealized depreciation		(1,825,940	)
Net unrealized appreciation (depreciation)	$	(97,729	)

The aggregate cost above includes prior fiscal year end tax adjustments.

(3) Derivative Contracts at 8/31/08

Futures contracts outstanding at 8/31/08

Description	Contracts	Value		Expiration Date	Unrealized Appreciation (Depreciation)
U.S. Treasury Bond (Short)	48	$	5,631,000	Dec-08	$	5,457
U.S. Treasury Note 10 yr (Short)	54		6,237,000	Dec-08		(3,986	)
					$	1,471

5

MFS California Insured Municipal Fund

Supplemental Information (Unaudited) 8/31/08

Swap Agreements at 8/31/08

Expiration		Notional Amount	Counterparty	Cash Flows to Receive	Cash Flows to Pay	Value
Interest Rate Swaps
12/17/18	USD	3,000,000	Merrill Lynch Capital Services	7-Day SIFMA	3.70% (fixed rate)	$	(79,950)
11/28/23	USD	3,000,000	Goldman Sachs International	7-Day SIFMA	3.75% (fixed rate)		(56,850)
12/17/23	USD	2,000,000	Morgan Stanley Capital Services, Inc.	7-Day SIFMA	3.87% (fixed rate)		(61,820)
10/08/28	USD	3,000,000	JPMorgan Chase Bank	7-Day SIFMA	3.7035% (fixed rate)		(16,950)
						$	(215,570)

At August 31, 2008, the fund had sufficient cash and/or other liquid securities to cover any commitments under these derivative contracts.

6

ITEM 2. CONTROLS AND PROCEDURES.

(a) Based upon their evaluation of the effectiveness of the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940 (the “Act”)) as conducted within 90 days of the filing date of this Form N-Q, the registrant’s principal financial officer and principal executive officer have concluded that those disclosure controls and procedures provide reasonable assurance that the material information required to be disclosed by the registrant on this report is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission’s rules and forms.

(b) There were no changes in the registrant’s internal controls over financial reporting (as defined in Rule 30a-3(d) under the Act) that occurred during the registrant’s last fiscal quarter that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

ITEM 3. EXHIBITS.

File as exhibits as part of this Form a separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2): Attached hereto.

Notice

A copy of the Agreement and Declaration of Trust, as amended, of the Registrant is on file with the Secretary of State of The Commonwealth of Massachusetts and notice is hereby given that this instrument is executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually and the obligations of or arising out of this instrument are not binding upon any of the Trustees or shareholders individually, but are binding only upon the assets and property of the respective constituent series of the Registrant.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Registrant: MFS CALIFORNIA INSURED MUNICIPAL FUND

By (Signature and Title)*	ROBERT J. MANNING
	Robert J. Manning, President

Date: October 15, 2008

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*	ROBERT J. MANNING
	Robert J. Manning, President (Principal Executive Officer)

Date: October 15, 2008

By (Signature and Title)*	MARIA F. DWYER
	Maria F. Dwyer, Treasurer (Principal Financial Officer and Accounting Officer)

Date: October 15, 2008

* Print name and title of each signing officer under his or her signature.

EX-99.CERT

EX-99.CERT

MFS CALIFORNIA INSURED MUNICIPAL FUND

CERTIFICATION

I, Maria F. Dwyer, certify that:

1. I have reviewed this report on Form N-Q of MFS California Insured Municipal Fund;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the schedules of investments included in this report fairly present in all material respects the investments of the registrant as of the end of the fiscal quarter for which the report is filed;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report, based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: October 15, 2008	MARIA F. DWYER
	Maria F. Dwyer
	Treasurer (Principal Financial Officer and Accounting Officer)

EX-99.CERT

MFS CALIFORNIA INSURED MUNICIPAL FUND

CERTIFICATION

I, Robert J. Manning, certify that:

1. I have reviewed this report on Form N-Q of MFS California Insured Municipal Fund;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the schedules of investments included in this report fairly present in all material respects the investments of the registrant as of the end of the fiscal quarter for which the report is filed;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of a date within 90 days prior to the filing date of this report, based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: October 15, 2008	ROBERT J. MANNING
	Robert J. Manning
	President (Principal Executive Officer)