We investigated the effectiveness of prophylactic administration of recombinant activated factor VII (rFVIIa) for cardiopulmonary bypass surgery in children under 1 year old with congenital heart disease (CHD) in a double-blinded, placebo-controlled study. The rFVIIa dose was 40 microg/kg and all patients also received standard haemostatic replacement therapy. The primary endpoint was the time to chest closure from neutralization of heparin with protamine sulphate as this could be most objectively and accurately measured during surgery. Secondary endpoints were volumes of transfused blood, platelet concentrates and fresh-frozen plasma. All adverse events were recorded. In the intention-to-treat analysis there were 76 patients (40 in rFVIIa group and 36 in placebo group). The demographics and severity of CHD were similar in both groups. No benefit of rFVIIa prophylaxis was found in the time to chest closure, which was significantly prolonged in the rFVIIa group (rFVIIa mean +/- SE, 98.8 +/- 27.27 versus 55.3 +/- 29.15, P = 0.0263). In the 41 patients available for a follow-up visit 6 weeks after discharge, the chest closure time was also prolonged in the rFVIIa group (P = 0.0515). There were no significant differences in the secondary endpoints. Adverse events were similar in both groups.