Autotransfusion system is a common method of reducing the need of intraoperative and postoperative homologous blood transfusion in cardiac operation. Between August 1991 and August 1993, a series of 51 adults undergoing open heart surgery was selected. Autotransfusion using Cell Saver [COBE Baylor Rapid Autologous Transfusion System was done with homologous blood transfusion in 15 cases [Group II or without homologous blood transfusion in 17 cases [Group III . The other 19 cases were taken without Cell Saver for control [Group I . The shed blood in the operative field, remained blood in the oxygenator after cardiopulmonary bypass, and blood drained from chest tubes in postoperative care were aspirated by means of a locally heparinized collection system. After the salvaged blood was washed and centrifuged, the processed blood subsequently reinfused. Composition of processed blood by Cell Saver was hemoglobin 16.9gm%, hematocrit 49%, RBC 5,140,000/ml, WBC 670/ml, and platelet 30,000/ml. In three group, hemoglobin, hematocrit, and platelet counts were decreased postoperatively, but no significant differences between three group. Postoperatively, the amounts of drainage from chest tubes was 543$pm$121ml in Group I, 809$pm$201ml in Group II, and 631$pm$147ml in Group III. In Group II, there was large amount of drainage compared with Group I [p<0.05 . The amount of homologous blood transfused was 1116$pm$219 ml in Group I, 791$pm$183 ml in Group II [p<0.05 . The homologous blood was not transfused in 17 cases [53% with Cell Saver.Preoperative and postoperative, coagulation parameters showed no significant differences between three group. And there was no complication related to Cell Saver. We conclude that the autotransfusion using Cell Saver is effective for reducing the homologous blood transfusion in cardiac surgery.