Objective: To determine the proportion of patients with HIV-related illness admitted to a medical ward. Design: A prospective study. Setting: Rubaga Hospital, the third largest hospital in Kampala, the capital of Uganda. Participants: A total of 449 patients admitted to the medical ward between September and November 1992. Results: Of the 449 patients, 390 (86.8%) agreed to provide a blood sample for HIV serology. Of these, 55.6% (95% confidence interval, 50.7–60.5%) were positive for HIV. Eighty-six (22.2%) of all patients [71 (33%) of the seropositives and six (3.5%) of the seronegatives] met the World Health Organization case definition for AIDS in Africa. The HIV-seropositives had a mortality rate of 1 7.4%, significantly higher (P= 0.00057) than the 5.8% rate observed in the seronegative group. The overall mortality rate was 13.7% and was significantly associated with HIV infection (P= 0.0005). Conclusion: HIV infection is a major contributor to morbidity and mortality in Uganda. Over 50% of the medical admissions were HIV-positive revealing the serious impact of HIV on the health-care system.