Ulcerative colitis (UC) is a chronic inflammatory bowel disease of the colorectum which results from a complex interplay between environmental, genetic and microbial factors. One-fifth of patients with UC will experience an acute flare requiring hospitalization. This is a medical emergency and requires prompt recognition and multidisciplinary management. In patients who fail first-line therapy after approximately 3-5 days of intravenous steroids, medical rescue therapy is indicated with either infliximab (IFX) or cyclosporine (CsA). Optimal dosing strategies for IFX are uncertain, with several retrospective studies suggesting an association between an intensified or accelerated IFX induction regimen and lower colectomy rates, although prospective studies are warranted. In patients not responding to medical rescue therapy, or in those with fulminant colitis, urgent colectomy is indicated. Longer prognosis is suboptimal, with half of patients requiring colectomy within 5 years of presentation with acute severe UC (ASUC).