The fibrinolytic response to venous occlusion was studied in 17 patients with inflammatory bowel disease: 7 with Crohn's disease, 10 with ulcerative colitis and compared with those obtained in 20 controls. Patients with inflammatory bowel disease showed decreased tissue-type plasminogen activator antigen release (t-PA Ag), no significant Von Willebrand antigen release (vWF Ag), and a residual plasminogen activator inhibitor activity (PAI activity) after venous occlusion. These modifications were more important in the evolutive colitis group compared with the remission group. Hypofibrinolysis, as defined by a defective t-PA release, and a residual PAI activity after venous occlusion might contribute to digestive and/or extra digestive thrombotic manifestations observed during the course of inflammatory bowel diseases.