 PHASE : IV TYPE OF STUDY : With direct benefit. DESCRIPTIVE : Multicentre, randomized, open label study. INCLUSION CRITERIA : Acute severe ulcerative colitis. OBJECTIVES : To compare the efficacy and safety of early administration of the combination therapy with infliximab and azathioprine with steroids and azathioprine in patients with acute severe ulcerative colitis treated with intravenous steroids. 