At Mulago Hospital in Kampala, Uganda, 270 consecutive patients at the dermatology and sexually transmitted disease (STD) clinic were enrolled in a study to evaluate the association of clinical STD syndromes and human immunodeficiency virus (HIV) infection. Female patients became sexually active earlier than male patients and were younger at marriage. Persons with a history of an STD during the preceding 5 years were more likely to be HIV infected (43%) than those without such a history (26%; OR 2.08, 95% C.I. 1.17, 3.73). Examination at the time of the visit demonstrated an association between genital ulcers and HIV infection in male and female patients (OR 2.21, 95% C.I. 1.08, 4.53, and OR 8.54, 95% C.I. 1.45, 87.55, respectively) but no association between HIV and urethritis or vaginal discharge. The etiologic fraction for HIV infection of genital ulcers was 0.218. Men with a history of contact with prostitutes were more likely to be HIV infected than those without contact (50% versus 28%, p less than 0.05), but once controlled for STDs, this relationship was no longer significant. This study confirms other studies from East Africa that have shown a relationship between genital ulcers and HIV infection. This finding, in the presence of no association between other STD syndromes and HIV infection, suggests that genital ulcers may be truly associated with HIV infection rather than a marker of high-risk activities.