Absorbable suture material for microvascular procedures may be superior to nonabsorbable sutures because no foreign body remains at the operative site after suture absorption. We compared Vicryl (polyglactin 910) to a nonabsorbable suture, Prolene, which has been noted to have minimal thrombogenic potency. Patency rates, aneurysm formation, histologies and growth of the distal limb were measured and compared in microvascular anatomoses of immature arteries. Using 8-week-old rats, both femoral arteries (mean external diameter .85 mm) were transected and reanastomosed, using 10-0 suture material (Vicryl and Prolene) on a BV75-3 needle. Thirty rats were included in the study and separated into three harvest groups which were harvested at 4, 8, and 12 weeks. Magnification arteriography of the femoral arteries was performed, as well as standard refill tests. Selected vessels were sent for histologic study using H & E stain. Foot lengths of the rats were measured and compared to preoperative lengths. Prior to harvest, the arteries in the growing animals increased in diameter by 35 percent. Overall patency rates were 68.2 percent for Vicryl and 59.1 percent for Prolene, a non-significant difference. Aneurysm formation was 9.1 percent for Vicryl, and 50.0 percent for Prolene, a significant difference (P less than 0.01). The arteries repaired with Vicryl showed less scar formation, less medial necrosis, and less subintimal hyperplasia. Distal limb lengths showed no difference in the Vicryl and Prolene groups, but both groups were statistically inferior with respect to the unoperated control group. Our study demonstrated Vicryl to be equivalent to Prolene with respect to patency rates, but superior with respect to aneurysm formation and histologic response.(ABSTRACT TRUNCATED AT 250 WORDS)