This study was undertaken to evaluate the myocardial preservation obtained by adding a Ca++ channel blocker, nifedipine, to cold potassium cardioplegia (4 mcg/Kg/L) in 24 patients undergoing coronary artery surgery. They were randomly divided into a treated (N) and a control (C) group. Significant differences between the two groups were noted in the cardiac arrest time (p less than 0.001), in the mechanical recovery mode (p less than 0.01) and in the inotropic support needed (p less than 0.01). Cardiac index increased significantly in group N but decreased in group C (p less than 0.01). Peripheral delta P/delta t and endocardial viability ratio (EVR) decreased in both groups. Coronary sinus and serum CK and CK-MB release were significantly lower in the treated group. ECG ischaemic changes occurred in 8 patients in group C but only in 1 case in group N (p less than 0.001). Arrhythmias occurred in 3 cases in group C (p less than 0.05). The incidence of perioperative myocardial infarction was not significant (2 cases in group C). These data suggest that nifedipine can protect the myocardial cell from ischaemic injury without depressing myocardial contractility or AV conduction.