A telephone survey of 1,592 Hispanic and 629 non-Hispanic white men and women aged 18-49, randomly selected from nine states in the northeastern and southwestern United States, found that married Hispanic men are more likely to have had two or more heterosexual partners in the previous 12 months than are married non-Hispanic men (18% and 9%, respectively). A large proportion of unmarried men (60% of Hispanics and 54% of non-Hispanic whites) report having had more than one partner in the past 12 months. After adjusting for other variables, the odds of having multiple partners are 2.5 times higher among Hispanic men aged 18-24 than among those aged 41-49 and 1.8 times higher among those who live in the Northeast than among those in the Southwest. Highly acculturated Hispanic men are less likely to have multiple partners than are less acculturated men. Among Hispanic women, those who are moderately or highly acculturated are more likely to have multiple partners (odds ratios of 4.9 and 8.4, respectively) than are less acculturated women. About half of men and women with multiple partners report always using condoms with secondary heterosexual partners.