Alimentary tract cytomegalovirus (CMV) infections of 24 patients were reviewed, including 19 with the acquired immune deficiency syndrome. CMV inclusion bodies (CMV-IB) were calibrated per mm2 of tissue. CMV-IB counts were correlated with biopsy site, inflammatory response, and clinical parameters. Colonic biopsies showed the highest counts. Biopsies of the right colon had about three times as many CMV-IBs as those of the left. Upper alimentary tract biopsies had low counts. Mesenchymal cells were most affected (97%); 35% were identified as endothelial and 6% as smooth muscle. Only 3% of CMV-IBs were in epithelial cells. Grades of inflammation, 1-5, correlated directly with CMV-IB counts up to grade 4. In grade 5 inflammation tissue destruction was so severe that CMV-IBs were difficult to recognize. Ulcers were demonstrated in more than half of all patients, either histologically or endoscopically. The inflammatory response was nonspecific, except for patchy infiltrates and the absence of lymphoid follicles, crypt abscesses, or granulomas. Gastrointestinal infections, such as shigellosis, candidiasis, mycobacteriosis, and cryptosporidiosis coexisted in 17 patients. No correlation was found between CMV-IB counts and severity of symptoms or length of survival. Alimentary tract CMV infections was the first manifestation of the acquired immune deficiency syndrome in 11 patients. Survival ranged from 2 wk to 19 months.