Recent clinical and pathologic studies have indicated that the pancreas is susceptible to ischemic injuries and ischemia may be an important factor in the pathogenesis of pancreatitis. But the significance of hyperamylasemia after cardiac surgery is controversial.Seventy three consecutive patients using cardiopulmonary bypass were prospectively studied to determine the clinical significance of serum amylase changes and hyperamylasemia after cardiopulmonary bypass in pediatric patients with congenital heart disease, and verify our hypothesis that the level of serum amylase may be an indicator of adequate perfusion of abdominal organs. Serum amylase level was not changed significantly immediately after cardiac surgery, but at the postoperative first and second days, the level was significantly higher than preoperative or immediate postoperative level, and at the third day, it decreased to the preoperative level [P = 0.067, Repeated Measure ANOVA . These changes have some clinical significance, and noticeably statistical significance between immediate postopreative and second day serum amylase levels [P [0.05 . But above sequential changes of serum amylase levels had no statistical relationship with those of BUN, Cr, SGOT, and SGPT. Sixteen patients[21.9 % developed hyperamylasemia . There was no significant difference between postoperative changes of serum amylase and variables in age, diagnosis, type of operation [palliative or curative , cardiopulmonary bypass time, and use of total circulatory arrest. But in the group with prolonged aortic cross clamp time[ 60 minutes , serum amylase level was elevated significantly at postoperative first day. There was no abdominal complication after cardiac surgery, and no difference in operative mortality between hyperamylasemia and normal value group.It is concluded that 1 the level of serum amylase increased significantly at postoperative first and second day after cardiac surgery, 2 the postoperative changes of serum amylase had no statistical relationship with that of BUN, Cr, SGOT, and SGPT in our study