The cases of acute pulmonary thromboembolism after coronary artery bypass surgery have been rarely reported in Japan. We, however, experienced 2 cases of them and lost them against intensive therapy. In Mitsui Memorial Hospital, 6 cases of pulmonary thromboembolism had been diagnosed in 1990 (0.074% in admission patients), four of the cases had occurred following surgical procedures. Its manifestations are deceivingly nonspecific and are difficult to distinguish perioperative myocardial infarction, pericardial tamponade, and pneumothorax, especially in postoperative states. We would like to emphasize that acute pulmonary thromboembolism is getting important problems also in Japan.