Ulcerative colitis is an inflammatory disorder that affects the rectum and extends proximally to affect a variable extent of the colon. The major symptoms of ulcerative colitis include diarrhea, rectal bleeding, the passage of mucus, and abdominal pain. Ulcer-ative colitis also may be complicated by many local and systemic disorders as extrain-testinal manifestations. Pyoderma gangrenosum is the most severe dermatologic com-plication associated with ulcerative colitis. It is a painful , chronic, ulcerating skin disease of unknown cause. Diagnosis is clinical, there being no accepted histological diagnostic criteria. Conventional therapy is empirical, usually with high dose corticosteroids, but var-ious other agents have been tried with occasional success including topical antibiotics, cyclosporine, disodium cromoglycate, and dapsone. This patient was treated with high dose corticosteroid (prednisolone 1 mg/kg/day) and discharged with clinical improvement. So we report this case with a literature review. (Korean J Gastrointest Endosc 19: 300 ∼305, 1999)