From July, 1977, to July, 1980, intermittent cold blood potassium cardioplegia was used in 208 patients undergoing aortic valve replacement. Aortic root injection of the cardioplegic solution at 10 degrees C was followed every 20 to 30 minutes by infusions of the solution through Silastic cannulas sutured in the coronary orifices or reinserted with each injection. Symptoms of myocardial ischemia developed in 6 patients 3 to 30 months postoperatively. Coronary angiography confirmed new stenoses of the left orifice (3 patients), left main trunk (1 patient), left anterior descending coronary artery (2 patients), circumflex coronary artery (1 patients), and right orifice (3 patients). Four patients underwent saphenous vein grafting procedures, with 2 deaths; 2 patients refused reoperation. A seventh patient with 80% stenosis of the circumflex coronary artery and a posterolateral myocardial infarction died 2 months after double-valve replacement. Intermittent cold blood potassium cardioplegia instead of continuous perfusion did not prevent coronary arterial injury. Injuries occurred in the distal coronary arteries as well as the orifices and were not prevented by withdrawal of the cannulas between injections. Tight-fitting cannulas and high-pressure injection should be avoided. A careful search for coronary arterial injury should be made in all symptomatic patients following aortic valve replacement.