This report presents a patient with corticosteroid-resistant active ulcerative colitis who was successfully treated by centrifugal leukocyte apheresis. A 15-year-old female who had suffered from left-sided ulcerative colitis for 16 months, was successfully treated with steroid therapy (predonine, 5 mg/day, for 12 months) . In April, 1998, fourteen months after remission of the first episode, the colitis recurred. This time, however, the patient did not respond to steroid therapy (predonine, 30 mg/day, for 4 days, followed by high-dose methylprednisolone). Therefore, she received treatment with centrifugal leukocyte apheresis in addition to steroid therapy (predonine, 60 mg/day). Apheresis (removal of 0.94 x10^10 leukocytes / treatment) was conducted once a week. After 5 weeks, the colitis remitted and the steroid dose was reduced. In spite of effectiveness of steroid therapy in therapy of ulcerative colitis, its adverse effects have been recognized well. Centrifugal leukocyte apheresis may be an effective alternative treatment for patients who do not respond to steroid therapy. Apheresis also reduced the adverse effects of steroid therapy.