Background: Arterial or venous thromboembolism is rarely encountered clinically as an extradigestive tract complication in inflammatory bowel disease (IBD). However, it is one of the important prognostic factors for IBD patients. The present study was designed to evaluate the relationship between pulmonary embolism (PE) and deep vein thrombosis (DVT) with coagulation-fibrinolysis markers in patients with active IBD. Methods: In 47 consecutive cases hospitalized due to active IBD [26 with Crohn’s disease (CD) and 21 with ulcerative colitis (UC)], we evaluated the disease severity, blood tests, pulmonary ventilation-perfusion scan (V/Q scan), and magnetic resonance venography (MRV) or conventional venography. Results: PE was diagnosed by V/Q scan in 5 (2 with CD and 3 with UC; 10.6%). DVT was diagnosed in 5 (2 with CD and 3 with UC; 10.6%). Of the 47 patients, 8 (17.0%) had venous thromboembolism (either PE or DVT), and 2 of them (4.3%) had both conditions. In UC patients, the thrombosis group was in more severe stages based on endoscopic grading than the nonthrombosis group. In all patients, the thrombosis group were older (50.3 ±14.3 years) than the nonthrombosis group (29.2 ±11.7 years). Fur thermore, the thrombosis group had higher thrombin-anti- thrombin III complex (13.1 ±17.7ng/ml) and D-dimer (964 ±1402ng/ml) values than the nonthrombosis group (5.3 ±5.5ng/ml, P = 0.0245, and 207 ±192ng/ml, P = 0.0016, respectively). There were no significant differences in leukocyte and platelet counts, C-reactive protein, and fibrinogen between the two groups. Conclusions: A high incidence of venous thromboembolism was suggested in Japanese patients with active IBD. We should be careful with thrombosis in treatment of IBD patients, especially those who are of older age and in more severe stages. Background: Arterial or venous thromboembolism is rarely encountered clinically as an extradigestive tract complication in inflammatory bowel disease (IBD). However, it is one of the important prognostic factors for IBD patients. The present study was designed to evaluate the relationship between pulmonary embolism ( PE) and deep vein thrombosis (DVT) with coagulation-fibrinolysis markers in patients with active IBD. Methods: In 47 consecutive cases hospitalized due to active IBD [26 with Crohn’s disease (CD) and 21 with ulcerative colitis (UC)], we Results: PE was diagnosed by V / Q scan in 5 (2 with CD and 3 with (with V and Q scan), and magnetic resonance venography (MRV) with conventional venography Of the 47 patients, 8 (17.0%) had venous thromboembolism (either PE or DVT), and 2 of them (4.3 %) had both conditions. In UC patients, the thrombos is group was in more severe stages based on endoscopic grading than the nonthrombosis group. (50.3 ± 14.3 years) than the nonthrombosis group (29.2 ± 11.7 years). Fur thermore, the thrombosis group had higher thrombin III complex (13.1 ± 17.7 ng / ml) and D-dimer (964 ± 1402 ng / ml) values ​​than the nonthrombosis group (5.3 ± 5.5 ng / ml, P = 0.0245, and 207 ± 192 ng / ml, P = 0.0016, respectively). There were no significant differences in leukocyte and platelet counts, C-reactive protein, and fibrinogen between the two groups. Conclusions: A high incidence of venous thromboembolism was suggested in Japanese patients with active IBD. We should be careful with thrombosis in treatment of IBD patients, especially those who are older age and in more severe stages.