We describe the clinical and histologic features of non-Hodgkin's lymphoma in 26 patients with human immunodeficiency virus 1 (HIV) infection. These represent 10 per cent of AIDS cases recorded in the Bordeaux area. Mean age was 42. Contamination was mostly related to homosexuality (50 per cent) and blood transfusion (27 per cent) with 5 female cases. The initial presentation of lymphoma was extranodal (69 per cent). Lymphoma spread was diffuse (65 per cent), involving the bone marrow (38 per cent), lymph nodes (35 per cent), central nervous system (27 per cent), oral and digestive mucosae (23 per cent), liver (19 per cent) and genital tract (12 per cent). Histologic types were of intermediate or high grade malignancy (88 per cent) with 38 per cent large, non cleaved-cell (centroblastic) subtype. Median survival was 4 months. Lymphoma caused death in 65 per cent of patients and opportunistic infection in 18 per cent. Lymphoma was the first manifestation of HIV infection in 10 patients (38 per cent) and was responsible for AIDS in 14 (54 per cent). Diagnosis of lymphoma could be established at an early stage on extranodal biopsy. In these patients a prolonged disease-free survival was obtained after chemotherapy alone or associated with radiotherapy.