Lymphomas are a relatively common complication of AIDS in western countries, but little is known of the impact of the AIDS epidemic in Africa on the risk of these tumours. To investigate the types of non-Hodgkin lymphoma (NHL) occurring in Kampala, Uganda, their association with Epstein-Barr virus (EBV), and how their risk is modified by HIV and other variables. A case-control study comparing NHL cases with age/sex-matched controls. Lymphoma cases included 50 histologically diagnosed adults (31 with validation and phenotyping) and 132 histologically diagnosed children (61 with validation and phenotyping). Controls were adults with cancers unrelated to HIV and children with non-infectious diseases. Most (90%) childhood lymphomas were EBV-positive Burkitt's lymphoma (BL), with no association with HIV. Adult lymphoma cases were mainly BL (mostly EBV positive) or diffuse B cell lymphomas (71%). Only a weak association was found with HIV infection; a more precise estimate was obtained with the total series (OR 2.2, 95% CI 0.9-5.1) than validated/phenotyped cases (OR 2.1, 95% CI 0.3-6.7). Higher socioeconomic status adults, who travelled away from home, or had a history of sexually transmitted diseases, appeared to have a moderately increased risk of lymphoma. Childhood lymphomas were predominantly endemic BL, the risk of which was not modified by HIV. In adults, the risk associated with HIV was much lower in Uganda than in western countries, possibly because of the poor survival of immunosuppressed HIV-positive individuals. Future studies will require careful attention to subtyping of lymphomas, to investigate the possible differences between them.