Ulcerative colitis in childhood is a rare disease in Japan. A 10-year-old male child was admitted to Okayama University Hospital with a chief complaint of mucous and bloody diarrhea. He had been treated conservatively in another hospital, but the symptoms had not improved. Barium enema examination revealed, from the sigmoid to the transverse colon, abnormal barium coating, numerous small niches, disappearance of the network pattern, and faint spiculations along the margins. Endoscopy demonstrated slight edema, hyperemia, easy bleeding and some purulent secretion. Biopsy specimens showed infiltration of lymphocytes, plasma cells and eosinophilic leucocytes in the mucosa. We made a diagnosis of ulcerative colitis. The patient responded poorly to Salazopyrin and Penicillin, but improved considerably with corticosteroids.