Acute severe ulcerative colitis (ASUC) is a potentially life-threatening presentation of ulcerative colitis that in nearly all cases requires inpatient management and coordinated care from hospitalists, gastroenterologists, and surgeons. Even with ideal care, a substantial proportion of patients will ultimately require colectomy, but most patients can avoid surgery with intravenous corticosteroid treatment and if needed, appropriate rescue therapy with infliximab or cyclosporine. In-hospital management requires not only therapies to reduce the inflammation at the heart of the disease process, but also to avoid complications of the disease and its treatment. Care for ASUC must be anticipatory, with patient education and evaluation starting at the time of admission in advance of the possible need for urgent medical or surgical rescue therapy. Here we outline a general approach to the treatment of patients hospitalized with ASUC, highlighting the common pitfalls and critical points in management.