BACKGROUND: Understanding racial/ethnic disparities in cancer screening by family history risk could identify critical opportunities for patient and provider interventions tailored to specific racial/ethnic groups. The authors evaluated whether breast cancer (BC) and colorectal cancer (CRC) disparities varied by family history risk using a large, multiethnic population-based survey. METHODS: By using the 2005 California Health Interview Survey, BC and CRC screening were evaluated separately with weighted multivariate regression analyses, and stratified by family history risk. Screening was defined for BC as mammogram within the past 2 years for women aged 40 to 64 years; for CRC, screening was defined as annual fecal occult blood test, sigmoidoscopy within the past 5 years, or colonoscopy within the past 10 years for adults aged 50 to 64 years. RESULTS: The authors found no significant BC screening disparities by race/ethnicity or income in the family history risk groups. Racial/ethnic disparities were more evident in CRC screening, and the Latino-white gap widened among individuals with family history risk. Among adults with a family history for CRC, the magnitude of the Latino-white difference in CRC screening (odds ratio [OR], 0.28; 95% confidence interval [CI], 0.11-0.60) was more substantial than that for individuals with no family history (OR, 0.74; 95% CI, 0.59-0.92). CONCLUSIONS: Knowledge of their family history widened the Latino-white gap in CRC screening among adults. More aggressive interventions that enhance the communication between Latinos and their physicians about family history and cancer risk could reduce the substantial Latino-white screening disparity in Latinos most susceptible to CRC. © 2011 American Cancer Society.