Antiphospholipid syndrome (APS) is a rare disease in which patients display prolonged coagulation test results in vitro , but usually develop thrombotic symptoms in vivo . Patients with APS are at increased risk of valvular heart disease or coronary vascular disease, conditions that often necessitate cardiac surgery via bypass. The management of anticoagulation during cardiopulmonary bypass (CPB) is particularly challenging in these patients because of the unique features of APS. Patients with APS are constantly at risk of arterial and venous thrombotic events. Therefore it is very important to maintain proper anticoagulation perioperatively, especially during CPB. In this paper, we present three successful cases of APS patients who underwent cardiac surgery with CPB.