Background: Activation of coagulation and fibrinolysis occurs in patients with inflammatory bowel disease. Our aim was to study the course of a marker for activation of the coagulation cascade, prothrombin fragment 1 + 2 (F₁₊₂), and fibrinolysis, fibrin degradation products (FbDP), in patients with ulcerative colitis and Crohn's disease before and during therapy with glucocorticoids. Methods: Twenty-seven patients with active ulcerative colitis and 42 with active Crohn's disease treated with glucocorticoids were studied. Plasma samples were drawn before, during, and at end of therapy or at time of treatment failure. F₁₊₂ and FbDP were measured with commercially available enzyme immunoassays. Results: Mean base-line concentrations of F₁₊₂