Myocardial metabolism and the current state of metabolic intervention under conditions relevant to cardiac surgery are reviewed. The rationale for metabolic support differs considerably in various settings of cardiac surgery. Although preventive measures are theoretically attractive, their use in the preoperative setting remains to be clarified. Amino acid enrichment of blood cardioplegia seems to be justified by an abundance of animal experimental data. In the postoperative setting of cardiac surgery, metabolic abnormalities may explain reversible myocardial dysfunction. Further, the combined effects of ischemia and the systemic neuroendocrine response to surgical trauma may adversely affect recovery. Amino acids, particularly glutamate, seem vital for metabolic recovery in this setting. Treating the relative shortage of glutamate occurring during this period by the administration of exogenous glutamate and counteracting the effects of the systemic neuroendocrine stress response by high-dose glucose-insulin-potassium are measures that have been shown to improve the metabolic state of the heart and subsequently myocardial performance.