A synthetic, monofilament, absorbable suture material, polytrimethylene carbonate, was tested to determine its suitability for use in arterial anastomoses. The material studied is a copolymer made of trimethylene carbonate and polyglycolic acid, with a retention time in the tissue of up to six months. In an experimental group of 12 mongrel dogs, using simple end-to-end anastomoses, aortic and femoral patch grafts of bovine heterograft material and iliofemoral bypass implants of 5 mm of expanded polytetrafluoroethylene prostheses were performed and arteriographically and histologically documented. Direct intraindividual comparisons were made with the absorbable (polytrimethylene carbonate) and nonabsorbable (polypropylene, expanded polytetrafluoroethylene suture) materials, a total of 108 anastomoses. No suture material-related complications such as ruptures or suture line aneurysms occurred. Polytrimethylene carbonate sutures led to less inflammation and scar tissue formation than polypropylene sutures. Complete absorption of the suture material by hydrolytic decomposition was followed by an almost complete regeneration in all layers of the vessel wall. Regeneration of the connective tissue structures of the media was noted. Initial associated reactions in the intima eventually disappeared. Both suture materials were equivalent histologically in the early months of the study, but after 10 month follow-up differences were observed, especially in the structure of the media, apart from the fact that polytrimethylene carbonate is absorbed completely after four to seven months.