Coronary arterial stenoses impose a constraint on the delivery of cold cardioplegic solutions conventionally perfused via the aortic root, resulting in uneven myocardial cooling and protection. Therefore the hearts undergoing coronary bypass operations show impaired cooling of the post-occlusive myocardial regions, and temperature gradients among different myocardial fields are registered after cold cardioplegic perfusion. We applied retrograde coronary sinus perfusion of cold cardioplegic solution in canine hearts with occluded multiple left coronary arterial branches to overcome the above-mentioned drawbacks, and a uniform left ventricular cooling was demonstrated by this technique.