Methods for adequate hemostasis against the dilutional coagulopathy with larger priming volume of pediatric cardiopulmonary bypass (CPB) are not yet standardized. The aim of this prospective, randomized study was to evaluate the hypothesis that fresh frozen plasma (FFP) given pre-emptively for pump priming could improve the postoperative coagulation profile in the pediatric patients undergoing cardiac surgery with CPB. 47 pediatric patients undergoing elective congenital heart surgery with CPB were randomly assigned to either control (C) or treatment (T) group, given 10% albumin or FFP for pump priming, respectively. Coagulation profile, estimated by coagulation factor assays and rotational thromboelastogram (ROTEM), was serially checked as follows: after anesthesia induction, after CPB weaning & heparin reversal, and 24 hours after ICU admission. Intraoperative surgical bleeding, chest tube drainage during 24 h of ICU stay, and perioperative transfusion requirement were measured. Perioperative care was at discretion of physicians blinded to the patient assignment. Values are expressed as median (1th, 3th quartile) & statistically evaluated with non-parametric methods. The patients aged 0.8-182.3 months, weighing 2.9-50.7 ���. After CPB weaning, fibrinogen level was higher in T group [127.5 ���/��� (100.5, 146.3) vs. 188 ���/��� (151, 209), p<0.001]. Moreover, clot strength, measured by calculated ROTEM parameter, MCE (maximal clot elasticity) was enhanced in T group at all aspects of blood coagulation (Table 1). Transfusion amount in T group, especially for FFP, was larger intraoperatively, [294.8 ��� (250, 397.5) vs. 500 ��� (430, 657.5), p<0.001]. In the ICU, however, more FFP was given in C group [44 ��� (0, 50) vs. 0 (0, 0), p=0.005]. Transfusion requirement in ICU was nearly twice in C group, but not statistically significant [72.5 ��� (9.5, 135.8) vs. 40 ��� (0, 95)]. For patients undergoing repeated surgery, FFP priming significantly reduced the weight-standardized amount of intraoperative bleeding [18.3 ���/��� (17.7, 20.8) vs. 9.9 ���/��� (9, 11.6), p=0.008], but limited number of the patients (4 and 7 for C & T group, respectively) could lessen the statistical power. FFP priming for pediatric patients undergoing congenital heart surgery with CPB was demonstrated to enhance the clot strength just after CPB weaning, thereby reducing the intraoperative hemorrhage especially in the repeated surgery patients, but clinical effectiveness requires further evaluation.