We identified 40 patients with malignant lymphoproliferative diseases (MLD) and HIV infection (seropositive) at a single Spanish university hospital. Thirty-two patients had non-Hodgkin's lymphoma (NHL), 6 primary central nervous system lymphoma (PCL) and 8 patients Hodgkin's disease (HD). Median age at presentation was 32 years. Four histopathological groups had distinct presenting clinical features: in 93% of the Burkitt-type lymphomas, the lymphoma itself was the AIDS defining criterion, while high and intermediate grade NHL other than Burkitt-like tended to have a more advanced HIV infection, demonstrated by antecedent AIDS criteria in 58% of these patients and a median CD4 positive cell count of 291 mm3; HD occurred in some patients without previous opportunistic infections (7/8 patients) but with median CD4 cells of 105 mm3; PCL occurred in a terminal stage of HIV infection, in patients with a low performance status, and frequent antecedent AIDS criteria. Objective response to chemotherapy could be seen in 62% of NHL patients and 100% of HD. Survival was adversely related to an antecedent diagnosis of AIDS, low performance status, and a primary localization in the central nervous system. Overall median survival was 5 months, but patients without the mentioned three adverse prognostic factors had a median survival of 10 months.