Elastase-inhibitory balance was studied during 36 cardiosurgical operations under artificial circulation, carried out in children aged 10,6±0,6 years with congenital heart diseases. It is estimated that imbalance in elastase-inhibitor system is mostly significant by the end of operation and in 2 hours after the operation. By the end of the first day increased level of protease inhibitors didn't compensate high elastase level, and elastase-inhibitory coefficient remained higher that before the operation combined with increased inflammatory markers.. It is drawn a conclusion that imbalance in protease-inhibitory system after the operation is a risk factor for complications and indicates necessity of its correction.