Background. Conventional treatment options for patients with severe steroid-refractory ulcerative colitis include intravenous cyclosporine, which is frequently burdened by toxicity or colectomy. Preliminary data suggest a benefit from anti-tumour necrosis factor alpha (Infliximab) therapy in patients with steroid refractory ulcerative colitis. Aim. To evaluate the efficacy of Infliximab In the treatment of severe ulcerative colitis refractory to conventional therapy. Patients and methods. A series of 13 patients with severe ulcerative colitis, refractory to therapy with methyl-prednisolone, 60 mg dally for seven or more days, were treated with a single intravenous infusion of Infliximab 5 mg/kg. Results and conclusions. Of these 13 patients, 10 (77%) had a clinical response to therapy defined by a clinical activity index less than or equal to10 on two consecutive days. In 2 patients (15%) total colectomy was necessary on account of clinical worsening whilst one patient refused surgery and was lost to follow-up. All patients who responded showed very rapid clinical Improvement, within 2 to 3 days of infusion, Infusion with Infliximab produced no significant adverse events. The mean time of follow-up was 10.1 months (range 5-12); during this time, 9 out of 10 patients (90%) maintained clinical remission and were able to discontinue corticosteroid therapy Infliximab appears to be an effective agent for inducing long-standing remission in refractory patients with severe ulcerative colitis.