The authors analyze the results of 220 applications of internal cold cardioplegia in 136 patients with ischaemic heart disease, treated surgically by aortocoronary bypass. The operation was performed under neuroleptanalgesia and artificial circulation with hypothermia (27.9 +/- 0.2 degrees C) and haemodilution (24.9 +/- 0.3%). On the basis of clinical examination, electron microscopy of the myocardial ultrastructure, and investigation of the myocardial metabolism (contents of glucose, lactate, pyruvate, free fatty acids, catecholamines, and oxygen in arterial and venous blood flowing out of the myocardium), they come to the conclusion that internal cold cardioplegia efficiently protects the myocardium during aortocoronary bypass and secures favourable conditions for the development of anastomoses between coronary arteries and venous shunts.