We report 2 homosexual patients with the acquired immune deficiency syndrome and histopathologic evidence for cytomegalovirus colitis. In each case, the initial endoscopic impression was Kaposi's sarcoma but the appropriate diagnosis was made by histologic demonstration of a cytomegalovirus vasculitis. Clinical manifestations may include diarrhea, abdominal pain, and hematochezia. Fulminant progression to gangrenous bowel was documented in 1 patient and was associated with histologic evidence of severe cytomegalovirus vasculitis. The pertinent clinical, endoscopic, and pathologic findings are reviewed.