Several investigators have explored the possibility of revascularizing the ischemic myocardium from the ventricular chamber. The high energy laser was investigated as a means to accomplish this based on the finding that the laser beam could produce small channels in the myocardium devoid of debris and scarring. The technique was investigated in four groups of mongrel dogs. In three groups the left anterior descending branch of the coronary artery was ligated and the myocardium exposed to laser treatment. The fourth group was the control, the LAD was ligated but laser channels were not made. In the three groups treated by laser, the myocardium was protected by the channels. In the control group all animals died within 20 minutes of LAD ligation. Animals in the first three groups were subsequently sacrificed at various intervals. Channels were visualized grossly, microscopically they were patent and endothelialized. The results indicate channels made by laser effectively protect the myocardium from acute coronary artery occlusion.