This study compares demographic characteristics, sexual risk factors for HIV/STI, and cultural predictors of sexual risk among 254 Dominican and 1,012 Puerto Rican women using outpatient health care in New York City. More Dominicans were born outside continental United States and were employed, whereas more Puerto Ricans were single and less educated. Both groups of Latinas exhibited low condom use with main and other sexual partners, perceiving their own and their partners' risk as low. Puerto Ricans were more heterosexually active, had more sexual partners, had higher incidence of STI and HIV than Dominicans. However, Puerto Rican women were more likely to use condoms with a sexual partner. Significant differences in sexual risk support the design of ethnically tailored HIV prevention interventions. (Contains 2 tables.)