The suture materials influence the success of microvascular anastomosis importantly. The purpose of this experiment is to observe the effect of absorbable suture material and nonabsorbable suture material in microvascular anastomosis. The study was carried out on one side of carotid arteries of fourty rats which were anesthetized intraperitoneally with urethane. The experimental procedures differed in two groups, Group A in which the carotid artery was sutured with 10-0 monofilament polyglycolic acid, Group B in which the carotid artery was sutured with 10-0 monofilament nylon. Gross and histological examination were used to compare the results of end to end suture above two suture material. The results were as follows. 1. Nylon had greater tensile strength and ease of handling than polyglycolic acid, but held knots poorly. 2. Polyglycolic acid had difficult handling and lesser tenslie strength than nylon, but held knots hardly. 3. Polyglycolic acid had high patency rate, some lesser tissue response than nylon.