The aim of this study was to determine the optimal parameters for an Argon laser (spot diameter equals 200 micrometers ) to obtain and reproduce vessel anastomoses. It was performed in 2 groups of Wistar rats. In the first group (89 shots on 10 carotids), the fluence was continuously adjusted from 30 to 3,000 J/cm2 in order to determine an optimal set of parameters (power from 90 to 200 mW, shot duration from 0.1 to 5 seconds, pulsed or continuous mode). In the second group, thirty end-to-end carotid anastomoses were evaluated by macroscopic, thermal and histological studies. The second group proved the efficiency of the selected parameters. Vessel welding was obtained with 100 mW, 3 seconds, continuous mode (fluence equals 950 J/cm2, irradiance equals 320 W/cm2) for a mean temperature of 77 degree(s)C corresponding to collagen denaturation. In the second group the patency rate was 93% (28/30) with 3 pseudo-aneurisms and 2 thromboses. Histological studies noted slight modifications of the media.