Diversion colitis is a benign inflammatory process that occurs in any part of the large bowel excluded from the fecal stream by a diverting colostomy. While most of the patients with diversion colitis usually are asymptomatic, a minority has abdominal pain and rectal discharge of blood or mucus. A 65-year-old Japanese man was diagnosed as having diversion colitis with ulcerative colitis at 4 months after subtotal colectomy. Corticosteroid and mesalazine enemas were started nonsynchronously. A proctoscopy after 2 months showed no response. Prednisolone injections were started at 1.0 mg/kg daily, but the mucosal inflammation still failed to improve. A combined mesalazine 1 g plus prednisolone sodium phosphate 20 mg enema was started once daily. The rectal bleeding and endoscopic findings improved. Finally proctectomy and ileal pouch-anal anastomosis were successfully performed. A combined mesalazine plus corticosteroid enema may be effective in patients with diversion colitis associated with ulcerative colitis.