Cytomegalovirus infection is usually reported in immunocompromised patients. In this study, apparently immunocompetent patients with cytomegaloviral colitis were reviewed. Records with a diagnosis of cytomegaloviral colitis from January 1989 to June 1996 were retrieved for analysis. Ten patients were included (median age 70 yr). The major presenting symptoms were diarrhea and hematochezia. Ulceration was the main macroscopic finding. Rectal bleeding was mostly self-limiting. Three patients developed local complications (rectovaginal fistula in two; rectal stricture in one). In the two patients with rectovaginal fistula, lymphocytes subsets and proliferative response were entirely normal. In the other patient, low B lymphocyte count and low response to mitogen were demonstrated. However, the immunoglobulins were not suppressed and rectal biopsies revealed noncaseating granulomas, suggesting activated cell-mediated immunity. In conclusion, a high index of suspicion is crucial for early diagnosis of cytomegaloviral colitis in patients with bloody diarrhea, even though obvious evidence of immunodeficiency is lacking.