Conducting research on the health of Hispanic populations in the United States entails challenges of identifying individuals who are Hispanic and obtaining good study participation. In this report, identification of Hispanics using a surname search and ethnicity information collected by cancer registries was validated, compared with self-report, for breast cancer cases and controls in Utah and New Mexico. Factors influencing participation by Hispanics in a study interview in 2000-2005 were evaluated. The positive predictive value of identification as Hispanic by cancer registry records and surname search was 82.3% for cases and 73.2% for controls. Hispanics who were correctly classified differed from those who were misclassified, reporting lower language acculturation and educational attainment. Older age was positively associated with success in contacting Hispanic controls (p(trend) < 0.0001) but negatively associated with cooperation with the interview (p(trend) < 0.0001). Community characteristics described by US Census data, including income, education, and urban/rural residence, did not significantly influence participation by Hispanic cases or controls. The authors conclude that a surname search efficiently identifies Hispanics, although individuals identified using this method are not completely representative. Recruitment of Hispanic cases and controls does not appear to be affected by selection bias related to community characteristics.