BACKGROUND Although 5% albumin (human serum albumin [HSA]) is widely used in cardiac surgery children, synthetic colloids may provide a valuable alternative. This study compared 6% hydroxyethyl starch (HES) 130/0.4 with HSA for volume replacement in this population. METHODS The study was a two-center, randomized, controlled, parallel-group, double-blind trial performed in children aged 2-12 yr undergoing elective surgery for congenital heart disease under extracorporeal circulation. The primary objective was to demonstrate equivalence between HES and HSA with regard to the total volume of colloid infusion for intraoperative volume replacement including priming of the extracorporeal circuitery. RESULTS In the per-protocol population, mean volume of colloid required until end of surgery was (mean ± SD) 36.6 ± 11.8 ml/kg body weight in the HES group (N = 29) and 37.0 ± 11.9 ml/kg body weight in the HSA group (N = 26; ratio of means HES/HSA = 0.98 [95% CI, 0.84-1.16]). Intraoperative fluid balance was less positive in the HES group (P = 0.047). No difference was found regarding hemodynamics, the use of vasoactive and inotropic drugs. Blood loss, erythrocytes transfusion, and renal function were not different between groups. The incidence of adverse events up to postoperative day 28 did not differ between the groups. CONCLUSIONS In pediatric cardiac surgery, HES showed equivalence to HSA with regard to volume replacement therapy in children aged from 2 to 12 yr. Although there was no suggestion of an imbalance of safety measures between HES and HSA, the study was not powered to provide any firm conclusions about safety of tetrastarch in this population.