The aim of this study is to a.) evaluate whether early serum infliximab levels are predictive of avoidance of colectomy, b) evaluate whether serum albumin levels correlate with serum infliximab levels, and c) evaluate whether serum tumor necrosis factor levels are inversely correlated with serum infliximab levels.||In patients hospitalized for severe ulcerative colitis and treated with high-dose infliximab, we predict that early serum infliximab levels (24, 48, and 72 hour) will be positively associated with clinical response and avoidance of colectomy.