Preoperative autologous blood donation has been shown to reduce homologous blood transfusion in cardiac operations, but there have been few reports of its use in children. Of 50 children aged 6 months to 5 years (weight, 6.1-14.8 kg) undergoing primary cardiac surgery for simple anomalies, 23 donated autologous blood before surgery, the other 27 were age and weight-matched controls. Two donations of 10 mL x kg(-1) each were collected via the femoral vein under mild general anesthesia 12 +/- 5 and 19 +/- 7 days preoperatively. No complications related to autologous blood collection were observed. Homologous blood use was significantly less in the group given autologous blood (4.3%) compared to the control group (44.4%). There was no significant difference in hemoglobin levels between groups before, during or after the operation. Preoperative autologous blood donation appears to be safe and effective in reducing homologous transfusions, even in children weighing less than 15 kg.