Abstract: Thirteen coronary arteries in 5 fresh cadaver hearts eonsisted of normal arteries or arterios with 75-100% stenosid. The occluded arteries were exposed with Nd-YAG laser until artery canalization or perforation appeared. 4 arteries totally occluded by artificially created thrombi and 3 arteries partially occluded by atherosclerotic plaque were successfully canalized with exposure of mean 149.3 and 252.3 joules respectively. Two of 4 arteries partially occluded by calcifid plaque were canalized with exposure of mean 304.8 joules. Other 2 arteries totally occluded by calcified plaque were not canalized.After energy exposure was increased, the artery walls were perforated.The experience suggests that the canalization of occluded arteries with laser is closely related to the type of diseased arteries. Successful rate of canalization is higher in the arteries occluded by artificially created thrombi and atherosclerotic plaque with Nd-YAG laser, but lower in that occluded by calcified plaque. Energy reguired for the artery canalization is different for various diseased arteries. The energy of exposure is less for canalization of arteries occluded by artificially created thrombi, and more for arteries occluded by calcified plaque, especially calcified plaque.