Among 47 patients with thrombotic thrombocytopenic purpura (TTP), 8 patients were diagnosed to have postoperative-TTP. Two patients underwent vascular surgery, 5 patients coronary artery bypass grafts, and 1 patient resection of myocardial sarcoma. Prior to surgery, all patients except one had normal hemograms and platelet counts, and blood smears showed no schistocytes. Five to 19 days after surgery, all 8 patients developed postoperative TTP, which clinical feature was characterized by unexplained progressive encephalopathy, thrombocytopenia, and microangiopathic hemolytic anemia. In addition, in 3 patients, progressive gangrene of the toes also developed. Four patients achieved complete remission following exchange plasmapheresis and 1 patient spontaneous remission. Due to complicated surgical settings after surgery, recognition of TTP was often delayed and it contributed to death in 3 patients despite treatment with exchange plasmapheresis. In view of occurrence of postoperative TTP following cardiac and vascular surgeries, pathogenic mechanism for postoperative TTP may be explained on the basis of injury of diseased endothelial surface and release of a humoral factor(s) that results in platelet aggregation in the capillaries and arterioles. Our experience with these cases indicates that TTP may occur as a serious complication of cardiac and vascular surgeries, and early recognition of the diagnosis and institution of exchange plasmapheresis are of paramount importance for favorable outcome.