Genital ulcers are implicated as a risk factor enhancing susceptibility to human immunodeficiencyvirus type 1(HIV-1)infection. Aprospectivestudytodeterminetheincidenceofand risk factors associated with acquisition of HIV-I in women with genital ulcers was done. HIV-1-seronegative women with genital ulcers attending a clinic for sexually transmitted diseases in Nairobi werefollowedto HIV-1 seroconversionovera6-month period. Of 81women, 10seroconverted to HIV-1. The crude 6-month incidence of HIV-1 infection was 12%. Risk factors associated with seroconversion included cervical ectopy (rate ratio [RR], 4.9; 95% confidence interval [CI], 1.5-15.6) and pelvic inflammatory disease (RR, 6.3; 95% CI, 1.9-20.4). Thus, cervical ectopy and pelvic inflammatory disease may increase susceptibility to HIV-1 in women with genital ulcers.