Laser angioplasty, using YAG-neodymium laser and a balloon catheter with monofiber quartz light guide (400 micron), introduced into its central canal, was performed in 8 dogs with thromboses of 11 femoral or carotid arteries. Average energy expenditure for recanalization was 26 +/- 4 J, with 4.9 +/- 0.3 W and exposure time of 5.1 +/- 0.7 s. Re-thrombosis developed after 5 to 10 days in all arteries, left in the circulation network after laser angioplasty. The latter part of the study is dealing with the assessment of the surface of femoral or carotid arteries of the dogs after laser exposure. This was done by quantitation of the adhered platelets after platelet-enriched plasma was circulated through vessels, whose inner surface was 1) intact, 2) de-endothelized, or 3) laser-damaged, using a scanning electron microscope. The thrombogenic index was 65-96, 85 and 66%, respectively, for the YAG-neodymium, argon and eximeric (XeCl) lasers.