Both AIDS-related infections and neoplasms of the gastrointestinal tract may be manifest by a clinical picture of acute abdominal disease. Severe abdominal pain may be seen in this population even in the absence of true surgical complications such as perforation, abscess formation, or obstruction. Localizing signs and symptoms are frequently misleading due to underlying immunosuppression, debilitation, and prior or current antibiotic use. CT assumes a critical role in evaluation of the symptomatic AIDS patient, providing evaluation of the entire abdomen and pelvis including lymph nodes, solid viscera, and the bowel itself. CT is thus the modality of choice for characterization of AIDS-related abdominal disease and for direction of appropriate therapy.