Successful surgery for pulmonary thromboembolism is reported, with emphasis on the indication and the necessity of cardiopulmonary bypass. Surgical treatment is indicated for patients with localized large thromboemboli not amenable to medical management. Surgery is also an option for patients in whom medical treatment is not effective. In the present case, the etiology was unknown and there was no history of deep vein thrombophlebitis of the legs, which suggested that the cause was an embolus from a lung tumor that had already been treated surgically. Histological examination revealed a fresh blood thrombus, 9 months after pulmonary resection. This patient had syncope at the onset of the pulmonary thromboembolism (major vessel type) without circulatory collapse.