The endoscopic findings in the colon and terminal ileum in eight cases of Yersinia enterocolitica enterocolitis infection were studied. The diagnosis was based on the isolation of Y. enterocolitica in the feces and/or elevated serum antibody titers to the organism. Total colonoscopy was performed between 7 and 38 days (mean, 24 days) after the onset of symptoms. In all patients, the terminal ileum was affected, followed by frequent involvement of the ileocecal valve and the cecum, and less frequently, the ascending colon. In the terminal ileum, round or oval elevations with or without ulcers were detected. Small ulcers were detected on the ileocecal valve and in the cecum. These findings were observed even 4 to 5 weeks after the onset of symptoms, suggesting a relatively long course for this disease.