Primary gastric non-Hodgkin's lymphoma (NHL) is a co-morbidity that can be observed during the clinical course of acquired immunodeficiency syndrome (AIDS). We evaluated the prevalence, clinical-evolutive aspects and form of endoscopic presentation of primary gastric NHL associated with AIDS. Two hundred and forty-three HIV patients were submitted to upper digestive endoscopy, with evaluation of clinical, endoscopic and histological data. A CD4 count was made by flow cytometry and viral load was determined in a branched-DNA assay. Six cases (five men; mean age: 37 years; range: 29-46 years) of primary gastric NHL were detected. The median CD4 count was 140 cells/ mm 3 and the median viral load was 40,313 copies/mL. Upper digestive endoscopy revealed polypoid (in four patients) ulcero-infiltrative (two patients) and ulcerated (two patients) lesions and combined polypoid and ulcerated lesions (two patients). Histology of the gastric lesions demonstrated B cell NHL (four patients) and T cell NHL (two patients). Five of the six patients died of complications related to gastric NHL. We concluded that primary gastric NHL is an important cause of mortality associated with AIDS.