Fifty Wistar rats were submitted to a carotid end-to-end microanastomosis by means of a Coherent 900 Argon Laser. The laser shots were of 300 mW in power output and 5 sec. in duration with an impact area of 150 microns in diameter. The anastomosis was obtained in 4 min. using on an average 19 impacts. The luminal patency was evaluated through doppler and angiography visualization regularly achieved from day 0 up to 7 months. Light, scanning electron microscopic and ultrastructural examinations revealed that, on day 0, endothelial damages never exceeded 100 microns in width in the vicinity of the anastomotic line. Collagenous denaturation was immediately observed in the media and adventitia. The fusion line became re-endothelialized from day 3 and a collagenous network was always present in the media on day 10. Furthermore a slight fibrosis of the adventitia increased the wall resistance. The patency rate was 76% complications such as disruption and aneurysm were due to the initial technical drawbacks.