To investigate HIV prevalence, sexual risk behaviors, and HIV testing among men who have sex with men (MSM) between 18 and 64 years old living in California. Cross-sectional study of a statewide population-based sample of MSM. Using data from the 2001 California Health Interview Survey (CHIS 2001), 398 men who self-identified as gay or bisexual were recontacted and interviewed by telephone for a follow-up study in 2002. Study participants were interviewed regarding their demographic characteristics and sexual behavior, HIV testing history, and HIV infection status. Those who self-reported as HIV-negative or of unknown status were offered an HIV test using a home urine specimen collection kit. HIV prevalence among MSM in California was 19.1% (95% confidence interval [CI]: 12.8% to 25.3%) with higher rates seen among the following subgroups: high school or less education (40.4%), annual income less than dollar 20,000 (35.0%), or history of ever injecting recreational drugs (40.3%). Young age and Hispanic or African-American race/ethnicity were associated with higher proportions of risky sexual behavior and lower HIV testing rates. HIV prevalence among MSM living in California continues to be high across the whole state, and population-based studies are needed periodically to complement findings from surveys using other sampling designs.