The clinical, radiographic and endoscopic findings in 16 patients with ischaemic colitis, all of whom were < 45 years of age, were analysed. The clinical features were characterized by an acute onset of abdominal pain and rectal bleeding, and persistent constipation prior to the onset of symptoms. Twelve of the 16 patients did not have any known predisposing factors. Barium enema examination and colonoscopy revealed longitudinal ulcers and oedema of the left side of the colon of these patients. These features were then compared with those found in patients with ischaemic colitis, who were > 70 years of age. Although the clinical symptoms, the site of involvement and the initial radiographic or endoscopic findings were similar between the two groups, the transient form of ischaemic colitis and constipation prior to the onset of symptoms were more frequently present in the young patients than in the old patients. These findings suggest that ischaemic colitis, which is not a rare condition even in young adults, is less severe in young patients than in old patients, and that constipation may be related to the pathogenesis of this disease in young adults.