We performed an open heart surgery for ventricular septal defect and right coronary cusp prolapse in a 5-year-old boy with hemophilia A. He has only 3.5% of factor VIII activity. This paper describes a successful perioperative management of hemophilia A. Previous infusion study of factor VIII concentrate showed an administration of 500 units of factor VIII increased its level from 3.5 to 25% two hours after the infusion. With this result we administered 1,500 units of concentrate 14 and 2 hours before the operation, factor VIII level was 201% after the induction of anesthesia. Sternotomy was uneventfully performed. Subarterial VSD was patch closed and right coronary cusp hung down into the defect was plicated. After intra cardiac repair, we administered 2,000 units of VIII factor concentrate, followed by an injection of protamin and its level was 240% at CCU. During the initial 3 postoperative day, patient was maintained with 1,500 units of factor VIII every 12 hours. Chest drains were removed on 2 postoperative day with no evidence of bleeding. Additional infusion of 1,000 units per a day was continued on postoperative days 4 through 17th. Subsequently factor VIII level was maintained more than 60%, so that we achieved successful perioperative course in a patient with hemophilia A.