Despite the widespread clinical success in open-heart surgery, bleeding after cardiopulmonary by-pass (CPB) has been a common problem especially in cyanotic congenital heart disease. Recently, there have been reports demonstrating that treatment with high doses of aprotinin reduces postoperative bleeding. We studied the effect of aprotinin on postoperative bleeding in patients with tetralogy of Fallot who had undergone total correction in the Department of Thoracic and Cardiovascular Surgery of the Hacettepe University Faculty of Medicine, and compared our results with those in the literature. Ten patients out of 20 in the study were given high doses of aprotinin and were compared with the remaining 10 patients who had not received the drug. Standard anesthesia, perfusion and surgical techniques were used in all operations. The total amount of bleeding in the aprotinin-treated group was found to be 1530 ml, while in the other group it was 4185 ml (p < 0.05). The total quantity of blood transfused in the aprotinin-treated patients was 3250 ml while it was 5865 ml in the control group (p < 0.05). No significant effect of aprotinin was found on Hb, Hct, PT, aPTT and thrombocyte counts (p > 0.05). However, the effect of the drug on bleeding and coagulation time was found to be statistically significant (p < 0.05).