Anti-coagulant management of cardiopulmonary bypass for the patient complicated with heparin-induced thrombocytopenia (HIT) is difficult. A woman of late 50's with a previous history of HIT was scheduled for mitral valve replacement, tricuspid valvuloplasty and coronary artery bypass graft. We knew that heparin antibody was negative by serologic and functional assay before the operation. According to the HIT guideline, we planned to use heparin only during cardiopulmonary bypass and to use argatroban for other catheters. Although the platelet count continued decreasing up to the 5th postoperative day unless the transfusion of platelets, heparin antibody was negative on the first postoperative day. But, it was thought that HIT would develop from 5 days to 10 days after using heparin. Therefore, we had to examine heparin antibody on the 5th postoperative day at least for the patients with a history of HIT. In the future, it is important to observe the patient carefully and examine heparin antibody.