This study compared the growth of vascular anastomoses performed with either polypropylene or polydioxanone sutures and with either continuous running suture or interrupted suture technique. Primary end-to-end anastomoses of the infrarenal aorta were performed in 38 puppies. Nineteen were performed with 5-0 polypropylene sutures; in ten all sutures were placed in continuous fashion, and in nine in interrupted fashion. The other nineteen were performed with 5-0 polydioxanone sutures; in ten the sutures were placed in continuous fashion, and in nine in interrupted fashion. The animals were subjected to the repeated aortograms at 2, 4, 8 weeks, 6 months and 1 year following operation. Each abdominal aorta was subjected to burst test, and pathological examination. All anastomoses were patent and tolerated burst-test (300 mmHg). Neither aneurysm nor dilatation of anastomotic site was observed. Anastomotic area was significantly smaller and more stenotic in the continuous polypropylene suture group than in other three groups at 8 weeks, 6 months and 1 year following operation. There was no significant difference among these three groups. No suture materials were observed in the polydioxanone suture groups after 6 months following operation. This study suggests that polydioxanone suture will be useful for the repair of cardiovascular anomalies where growth of the suture line is required.