The purpose of this study is to evaluate the contact Nd:YAG laser system for vasal anastomosis in the animal model. Eighteen mongrel dogs were used. In this study, two major groups--control and laser--were defined. In the control group, vas anastomoses were performed with conventional microsurgical technique in six dogs. In the laser group, we performed contact laser assisted vas anastomosis (CLAVA) in 12 dogs by means of a contact Nd:YAG laser with synthetic sapphire probe (ERP4), emitted 2.0 sec pulse duration of minimum 1 watt to maximum 10 watts power. The time needed for completion of the vasal anastomosis in CLAVA group was 2-3 min; in the control group, approximately 25 min. The patency rate did not differ in these two groups; however, microscopic sperm granuloma formation was 16.7% (2/12) in the control group but 0% (0/12) in the CLAVA group. In conclusion, CLAVA is a fast and simple technique for vasal anastomosis and there were no significant complications, sperm granuloma, or even significant swelling or hematoma in any animal in this experiment.