Coagulants have been used for a long time to promote the hemostasis during operation. We have carried out the study to see the effect of the thromboplastin preparation. Thrombokinase, on the coagulation mechanism, thrombin time, partial thromboplastin time, Ca++, and operation time and amount of bleeding in the twenty patients undergoing laminectomy or femur fracture operation. The patients were divided into two groups, in the control group(n=10), disllied water 20ml, and in the Thrombokinase group(n=10), 20ml of Thrombokinase(4 amles) was administered intravenously during 5 minutes. The results were as follows: 1) Prothrombin time and partial thromboplastin time were significantly prolonged in the control group compared to the Thrombokinase group(p<0.05). 2) In the Thrombokinase group, the duration of operation was shorter and the amount of blood loss was less than in the control group, but there was no significant statistical difference(p>0.05).3) There was no change in either blood pressure or pulse rate and also no side reaction during or after the Thromobkinase injection.