We have performed one case of autotransplantation and 11 cases of orthotopic homotransplantation using Korean mongrel dogs, and have scrutinized the hematologic and hemodynamic results. The mean weight of recipients was 15.42*1.2kg and varied from 14kg to 20kg. During the operation, anesthesia and other technical procedures including cardiopulmonary bypass were similar to the usual methods in human cardiac transplantation. It was found that the hematologic values were similar to those of human beings although there was wide variance. Hemodynamically the mean systolic and diastolic arterial pressures were 165.0* 12.9 mmHg and 100.0 *11.8 mmHg respectively, and the mean heart rate was 155.5*23.5/min. All cases died within 24hrs, and the mean survival in all but 6 cases where operative death occurred was 6.83*8.01 hrs[range 2-21 hrs]. The major causes of deaths were bleedings in 7 cases, failure to protect myocardium during the procedure in 2 cases, pulmonary edema in 1 case and multiorgan failure in 2 cases. From the above results we concluded that the most frequent complication was bleeding, and the cardiopulmonary bypass flow of 50-500ml/kg min was not suitable to the dog in CPB. In further experiment after this study, the technical and the bypass flow was increased. Bleeding was not significant. And the immunosuppresion during operation and postoperative period was tried.