Disorders of glucose metabolism were investigated in 177 patients undergoing cardiac surgery. In group I patients, the cardiopulmonary bypass (CPB) priming fluid contained glucose. Patients in group II received neither glucose nor insulin during the operation. Group III received insulin-glucose therapy OGT) during the operation (insulin, 1 U/kg/h, glucose, 0.5 g/kg/h). At the onset of CPB in group I, hyperglycemia was produced by the glucose load and by a relative reduction in insulin secretion. In group 11, the start of the operation was accompanied by a rise in the titer of insulin antibodies. IGT resulted in normalization of the blood glucose level after CPB and stability of the insulin antibody titer during the investigation. The indices of myocardial contractility in group III were better than those of the “glucose free” group II before and after CPB. In group II, indices of β-cell function were moderately depressed 16 to 18 hours after the operation. Insulin and c-peptide level measurements demonstrated insulin production in group III on the first postoperative day. The results demonstrate that IGT has some potential benefit for glucose metabolism and myocardial function during cardiac surgery.