During a 6-mth period in 1975, 102 patients undergoing scheduled coronary artery bypass grafting were studied by both conventional ECG and heart-specific enzymatic methods to evaluate the incidence and estimate the extent of myocardial damage associated with an anesthetic management protocol using halothane as a primary agent with adjuvant agents. Anesthetic interventions were made to maintain heart rate and systolic pressure at resting levels or below the heart rate systolic pressure product documented during exercise-induced angina. These interventions included adjustment of halothane concentration in all patients, the use of adjuvant agents in 88.2%, vasodilators in 26.5%, and the precardiopulmonary bypass use of vasoconstrictor or cardiostimulants in 9.8%. There were 2 early postoperative deaths. ECG evidence of infarction was observed in 4 surviving patients. Sustained release of heart-specific CPK-MB isoenzyme occurred in 78% of surviving patients. Isoenzyme activity was detected in only 1 patient prior to cardiopulmonary bypass (CPB), in 1 patient during CPB, and in all others after termination of CPB. The extent of myocardial damage as estimated by integrating CPK-MB values over time was directly related to number of vessels grafted and to aortic cross-clamp and CPB times. The ECG and enzymatic data both document a low level of myocardial damage associated with this anesthetic management protocol.