Purpose: Little research has been reported to date on the usefulness of olprinone in pediatric cardiac surgery, and no standard pediatric infusion protocol is currently established. Our study sought to confirm that the regimen described herein rapidly achieves the requisite plasma olprinone concentrations. Methods: For the purposes of our study, we enrolled 13 patients: 7 biventricular repair candidates and 6 Fontan-type operation candidates. We administered a continuous infusion of olprinone to our study subjects at 0.3 μg/kg/min with no loading dose starting approximately 30 minutes (min) before weaning from cardiopulmonary bypass (CPB). We performed blood sampling at 15, 30, 45, 60, 90, and 120 min after the start of infusion and at the same elapsed intervals after separation from CPB. We measured plasma olprinone concentrations using ultra-fast liquid chromatography. Results: We observed effective plasma olpri-none concentrations (>20 ng/ml) at 30 min after weaning from CPB, or at 60 min after the start of infusion. Conclusion: We conclude that continuous olprinone infusion at 0.3 μg/kg/min without a loading dose initiated immediately after the release of aortic cross-clamping or immediately after the completion of all surgical procedures quickly and reliably achieves effective plasma concentrations.