This study was designed to determine whether laser energy could be used effectively to resect atherosclerotic plaque through an endoscope in a live animal model. Twelve adult Yorkshire swine with infrarenal aortic atherosclerosis had a 2.5 mm and/or 3.2 mm diameter fiberscope passed into the aorta from the femoral artery after proximal aortic balloon occlusion. Endoscopic argon laser resection of the atherosclerotic plaque was then attempted in eight pigs with an argon laser fiber (60 to 400 microns). We were able to visualize the raised atherosclerotic plaque in all 12 pigs with the larger 3.2 mm diameter fiberscope, which was easily passed into the aortoiliac system from the 4 mm diameter femoral vessel. The articulating end feature enhanced maneuverability within the lumen and allowed laser fiber direction. The 2.5 mm endoscope did not allow adequate visualization in any pig since the vessel could not be cleared of blood. The 2.5 mm endoscope was also passed from the femoral artery distally into the hind limb and still did not allow adequate visualization of the vessel wall because of persistent luminal blood. The 3.2 mm endoscope enabled vessel wall visualization distal to the femoral artery when the proximal artery was occluded. No aortas were grossly perforated by the laser energy. In all pigs undergoing endoscopic laser resection, raised plaques were removed both grossly and histologically, although the plaque edges were carbonized and frayed as well as vaporized. With the small spot size of the argon fiber, channels were drilled through plaque, frequently with incomplete recanalization of the lumen.(ABSTRACT TRUNCATED AT 250 WORDS)