Experience with laser angioplasty in 16 coronary arteries in 9 cadaver hearts is presented. Coronary obstructions were due to experimentally created thrombi as well as to naturally occurring calcified plaques. Successful laser angioplasty was achieved in 14 of 15 arteries. One artery was sacrificed to determine factors necessary for deliberate perforation of the arterial wall. This procedure required more than 30 seconds of laser energy at 3.0 W with the catheter tip almost perpendicular to the wall. Penetration of the arterial wall occurred only in the second left anterior descending artery which was plaque-occluded because of operator inexperience.