This study was undertaken to hemodynamically determine the differences of myocardial protective effect between crystalloid and blood cardioplegic solution. Twenty nine children undergoing cardiac operations due to cyanotic congenital heart diseases were randomized into two groups receiving crystalloid or blood cardioplegia. Cardiac indices and other hemodynamic datum were examined postoperatively. Although there was no statistical differences between groups, postoperative stroke volume indices and left ventricular stroke work indices were slightly better with blood cardioplegia. We also found that postoperative left atrial pressures[p=0.0003], central venous pressures[p=0.004], and heart rates[p=0.014] were significantly lower with blood cardioplegia. The fact that relatively lower ventricular preloads [left atrial pressure and central venous pressure] were required to provide adequate cardiac output in blood cardioplegia group suggested superior myocardial protective effect of blood cardioplegic solution.