The relation between Plasmodium falciparum malaria and symptomatic human immunodeficiency virus 1 (HIV-1) infection was investigated in paediatric and adult patients in Kampala, Uganda, from 1987 to 1989. Both infections contributed largely to hospital morbidity. Of 1527 clinically suspicious in-patients, 61% were positive for HIV-1 infection. 52% of patients with positive HIV-1 serology fulfilled the World Health Organization clinical case definition for acquired immune deficiency syndrome (AIDS) in Africa. No association could be found between HIV-1 infection and malaria either in paediatrics or in adults. P. falciparum parasitaemia was present in 18% of all patients and no differences in prevalence of malaria infection or in parasite density could be demonstrated between HIV-1 positive and HIV-1 negative patients. The comparison of clinical symptoms showed typical differences in AIDS-related morbidity but no difference in malaria-specific morbidity. Also, the response to malaria treatment was the same in HIV-1 positive and HIV-1 negative patients. P. falciparum malaria does not appear to act as an opportunistic agent in AIDS patients in Uganda.