Background and aims: The mortality in severe episodes of ulcerative colitis (UC) has been reduced from 31-61% in the 1950 to 1-3%. Nevertheless it remains high in non specialist centers. Simple criteria are necessary to predict the outcome of seve re ulcerative colitis. Methods: 14 patients hospitalized for severe disease (Truelove and Witts criteria) from 1996 to 2000 were retrospectively analyzed. Patients were divided into two groups: 1. Group A: patients with severe disease surgically treated. 2. Group B: patients with severe disease responders to medi cal therapy. Sex, age, length of steroids medical therapy, fever, stool fre quency, CRP, ESR, haemoglobinemia, leukocytes, serum albumin values in the three days before the operation or during the hospitalization were collected. Results: total colectomy with ileostomy was necessary in 8 patients (57.1%), while 6 patients (42.9%) were respon ders to medical therapy. No perioperative mortality was recorded. Stool frequency, CRP, ESR, haemoglobinemia, serum albumin were signifi cantly related to surgical operation. Conclusions: 1. No uniform criteria of «severe attacks» are clearly defined in Literature. 2. The length of pre-operative medical therapy has a ten dency to be too high (in our series 19+8.2 days). 3. Stool frequency, CRP, ESR, haemoglobinemia, serum albumin were significantly modified in operated patients.