Approximately 15% of patients with ulcerative colitis have a severe attack requiring hospitalization at some time during their illness. This treatment leads to a remission in 60-80% of patients and non-responders may require a total colectomy. Mortality in severe episodes of ulcerative colitis decreased from 31-61% in the 1950s to 5-9% in the 1960s thanks to the introduction of steroids and to a policy of early colectomy. Recently, some new drugs have been shown to be effective in the treatment of severe steroid-refractory ulcerative colitis. This review concentrates on the clinical evaluation, prognostic factors and new developments in medical therapy in severe ulcerative colitis. A retrospective evaluation of a consecutive series of patients with severe ulcerative colitis admitted to a Gastroenterology Department in Torino, Italy, is also reported.