Coronary artery bypass grafting was performed in 166 patients with severe coronary artery disease using retrograde continuous cold blood cardioplegia (RC-CBCP) during the last 3 years and 8 months. In this study, myocardial protection was assessed from the aspect of enzymatic analyses and clinical results of these patients. Six hospital deaths were not related to the myocardial protection. Even in the groups of patients with medically refractory unstable angina, multiple occlusion of the coronary artery, low cardiac function and left main trunk lesion, RC-CBCP provided excellent protection of the myocardium and satisfactory results of operation as well as in each control group. Consequently we conclude that RC-CBCP affords safer and more effective myocardial protection in patients with severe coronary artery disease.