Background: Recently, many cardiac centers have been using aprotinin to reduce operative bleeding in cardiac operations using cardiopulmonary bypass. A variety of reports have confirmed the effectiveness of the drug in cardiac operations. In addition to the operations which could be considered to cause severe operative bleeding such as redo operation, long cardiopulmonary bypass operation and etc, the use of aprotinin is increasing in the field of primary cardiac operations. Varying doses of regimen have been introduced since the first report by Royston et al, and also various opinions on the effectiveness and safeness of the each regimen have been reported. We reviewed our own experience of the full dose aprotinin regimen(Hammersmith regimen) retrospectively. Material and Method: From October 1994 to February 1998, 40 cases of cardiac operative patients were randomized into two groups: aprotinin group(20 patients) which received a full dose aprotinin regimen and control group(20 patients) which did not receive aprotinin. To evaluate the degree of bleeding decrease, we analysed and compared the amount of postoperative 6 hours and 24 hours bleeding in the each group. To confirm the renal dysfunction, we measured the postoperative creatinine level. Result: In the amount of postoperative 6 hours bleeding, a statistically significant bleeding decrease was demonstrated in the aprotinin group compared to the control group(aprotinin group: 186${pm}$40cc, control group:409${pm}$69cc, P=0.010). Similar result was observed in the postoperative 24 hours(aprotinin group:317${pm}$53cc, control group: 671${pm}$133cc, P=0.024). Conclusion: We concluded that full dose regimen of aprotinin can remarkably reduce postoperative bleeding in cardiac operations without significant renal dysfunctions.