The effects of nicorandil (2-nicotinamidoethyl nitrate, SG-75) on the conductive coronary artery were studied and compared with the effects of nitroglycerin and nifedipine. In isolated perfused canine heart preparations with a support dog, nicorandil produced a decrease in the resistance of the conductive coronary artery at reduced perfusion pressures, whereas nitroglycerin had similar effects even at normal perfusion pressures. In anesthetized closed-chest dogs, nicorandil and nitroglycerin produced an increase in the diameter of the conductive coronary artery (nicorandil < nitroglycerin). Nifedipine failed to produce dilatation of the conductive coronary artery in both preparations. In isolated ring preparations of conductive coronary artery, all three compounds produced relaxation of the potassium-induced contracture, but only nicorandil and nitroglycerin reversed the lanthanum-induced contracture.