Thromboembolic disease is a significant cause of morbidity and mortality in patients with inflammatory bowel disease. The reported incidence is 1-6%. The most common thromboembolic complications are deep venous thrombosis of legs and pulmonary thromboembolism. Cerebral thrombosis, portal vein thrombosis, retinal venous thrombosis and arterial thrombosis were also reported. We experienced a case of ulcerative colitis complicated with pulmonary thromboembolism. The patient was a 70-year-old woman who was diagnosed as ulcerative colitis on colonoscopy. We used prednisolone and sulfasalazine for the treatment of ulcerative colitis. Twenty five days later, she complained of abrupt dyspnea and chest pain. Chest CT and ventilation-perfusion scan revealed a thromboembolism in both lung. After the treatment of heparin & warfarin therapy, follow-up chest CT showed much regressed pulmonary thromboembolism. We report a 70-year-old woman with ulcerative colitis complicated with pulmonary thromboembolism and treated with heparin & warfarin therapy successfully.