Two synthetic absorbable sutures were implanted in rats for a comparative evaluation of breaking strength, tissue reaction and absorption. Polyglactin 910 suture was stronger than polyglycolic acid suture in both sizes tested and at all time periods from zero to 35 days. Both suture types elicited minimal tissure response. Based upon histologic examination, virtually all remnants of the polyglactin 910 were absorbed by 90 days, while considerable quantities of polyglycolic acid persisted at 120 days. The difference in absorption rates was a highly significant feature of the comparative biologic profiles of the two suture materials.