This study was a cross-sectional analysis of different risk and cofactors for genital human papillomavirus (HPV) infection among 302 women in four ethnic groups at 10 clinic sites. Ethnicity, rather than HPV status, accounted for most of the differences among the groups on five risk factors: age at first sex, number of lifetime sexual partners, number of partners' sex partners, number of 'once only' sex partners, and number of 'long-term' sexual relationships. There were also ethnic differences in three of four cofactors, which may contribute to progression of HPV infections, namely, age when women began taking oral contraceptives and duration of use, number of years smoked cigarettes, and number of other sexually transmitted diseases. Women with more than four lifetime sex partners, more than two 'once only' sex partners, and/or women who took oral contraceptives for more than 4 years had a higher prevalence of HPV infection. Major risk and cofactors for HPV infection of each ethnic group are described and compared with other HPV studies.