Pediatric open heart surgery is associated with the usage of cardiopulmonary bypass. The circuit is primed with blood products because of risk of excessive hemodilution. The aim of the study was to prove the safety of open heart surgery on cardiopulmonary bypass without the use of blood products in the pediatric group. In this study, 78 patients with atrial septal defect (ASD type II) were enrolled and underwent elective atrial septal defect repair between the years of 1999 and 2003. The group I included 37 children aged from 3 to 16 years (8.79 +/- 4.45) who weighed from 13 to 68.8 kg (29.93 +/- 15.00). In this group, the transfusion of blood products during the surgery and postoperative course was avoided. Blood products were used in a control group (group II 4.1 patients) both during and after surgery. Children from this population ranged in age from 2.5 to 17 years (8.41+/- 4.18) and weighed from 11.5 to 59.7 kg (26.99 +/-12.95). For statistical analysis the t-Student test and U Mann Whitney test were used. The length of stay in the intensive care unit (1.18 +/- 0.47 vs 1.20 +/- 0.61 days) and total hospital stay (8.91 +/- 3.05 vs 10.05 +/- 4.28 days) did not differ statistically between the groups. Values of haematocrit and hemoglobin levels were statistically lower in group I during the postoperative course compared to the control group (intraoperative Hct: 19.43 +/- 4.93 vs 23.37 +/- 4.68%, p < 0.001), but these levels did not correlate with the occurrence of hypoxic, neurologic or coagulation complications. Directly after the surgery, group I had significantly higher platelet and leucocyte counts compared to the control group. There were no differences between the confronted populations in regard to postoperative bleeding (4.61 +/- 2.24 vs 4.76 +/- 1.75 ml/kg). The avoidance of using blood products in pediatric patients during open heart surgery with cardiopulmonary bypass is found to be safe, is not correlated with an increased surgical risk, and does not result in a prolonged hospital stay.