To clarify the prevalence and characteristics of gastrointestinal malignancy in patients with AIDS, we reviewed the demographics and clinical features of patients with AIDS and gastrointestinal neoplasms seen at North Central Bronx Hospital and Montefiore Medical Center during the past 8 yr. Malignant neoplasia complicated AIDS in 108/869 (12%) of the cases in our study. Most common was Kaposi's sarcoma (KS) (60%), followed by lymphoma (35%) and miscellaneous tumors (6.5%). The gastrointestinal tract was involved in 35/108 (32%) of patients with AIDS and neoplasia. Gastrointestinal tract involvement with KS usually was silent, although present, in every patient with KS who underwent autopsy. Lymphoma was most commonly non-Hodgkin's, and often produced symptoms. Uncommonly, the gastrointestinal tract was the primary site of neoplasms other than KS or lymphoma.