A 16-years-old femele was admitted ti our hospital because of lower abdominal pain and bloody stool of sudden onset. Laboratory studies showed WBC 10400and other findings were almost normal. Barium enema oerformed on the second day after onset showed stenosis, irrsgularity and ' thumb-printing ' in the descending colon. At colonoscopy, a longitudinal ulcer was revealed on the same lesion of the descending colon. Biopsy specimens from the lesion showed disappearance of glands, goblet cell depletion, edema and eosinophilic exudates. On 5th day after onset, subjective symptoms disappeared. A repeated colonoscopy on 6th day after onset showed almost normal mucosa without ulcer scar. This case was diagnosed as a transient ischemic colitis of Marstons' classification.