Ulcerative Colitis (UC) is a chronic inflammatory disease involving the colon, with alternating periods of remission and activity. Exacerbations can be severe and associated with complications and mortality. Diagnosis of severe UC is based on clinical, biochemical and endoscopic variables. Patients with severe UC must be hospitalized. First line therapy is the use of intravenous corticoids which achieve clinical remission in most patients. However, 25% of patients will be refractory to corticoids, situation that should be evaluated at the third day of therapy. In patients without response, cytomegalovirus infection must be quickly ruled out to escalate to second line therapy with biological drugs or cyclosporine. Total colectomy must not be delayed if there is no response to second line therapy, if there is a contraindication for second line therapies or there are complications such as: megacolon, perforation or massive bleeding. An active management with quick escalation on therapy allows to decrease the prolonged exposure to corticoids, reduce colectomy rates and its perioperative complications.