Our objective was to determine the prevalence of HIV and the distribution of HIV-related diseases among adult, medical inpatients. Consecutive admissions were recruited and a single ELISA assay was used to determine HIV infection. Demographic and clinical details were extracted from clinical records. Of 507 patients, 54% were infected with HIV of which 84% had AIDS. HIV-infected patients were significantly younger (34.9 years) than uninfected patients (47.1 years) and had significantly higher risks for oral/oesophageal candidiasis (risk ratio [RR] 18.6), generalized lymphadenopathy (RR 7.1), unexplained fever (RR 7.0), chronic diarrhoea (RR 6.2) and pulmonary tuberculosis (RR 3.1). Pulmonary tuberculosis was present in 56% of HIV cases. Mortality was 22% for HIV cases and 9% (P=0.016) for others. The mean length of hospital stay was the same for HIV-infected and uninfected patients. AIDS is the most common reason for admission to adult medical wards and will increasingly limit the number of beds available for non-AIDS patients.