Deep vein thrombosis and pulmonary thromboembolism have been common illness even in Japan and are receiving increased social as well as medical attention, especially during postoperative period. Vital Statistics of Japan compiled by Ministry of Health, Labor and Welfare indicated that the number of patients who died of pulmonary thromboembolism had increased about ten-fold in this half a century. The most effective way of reducing unexpected death from venous thromboembolism is to institute a comprehensive institutional policy of primary prophylaxis and early diagnosis in patients at risk. The diagnostic strategy has changed along with the improvement especially of venous ultrasound sonography and multidetector-raw CT. The diagnosis of venous thromboembolism is now more noninvasive and accurate. However, we still have no screening test, although symptoms and signs of venous thromboembolism are more complex in perioperative period. Therefore, we need to observe more carefully. We have to find venous thromboembolism among patients with single leg swelling and pain, or sudden dyspnea and transient loss of consciousness, and link to this finding diagnostic algorithm.