Tracheal anastomoses were performed in 19 lambs (mean age 4 weeks, mean weight 9.8 kg) to compare polydioxanone (PDS) and polyglactin 910 (Vicryl) suture material (Ethicon, Inc., Somerville, N.J.) and simple continuous and simple interrupted suture technique. Each animal had two anastomoses with full-thickness bites for both suture techniques. Animals were killed at 4 months (n = 6) or 8 months (n = 5). Eight animals died before they were scheduled to be put to death (mean 6 weeks postoperatively). Transverse sections of the trachea were taken at the level of the anastomoses and three tracheal rings above and below each anastomosis. The cross-sectional area of the tracheal lumen of these transverse sections was measured with a computerized digitizing tablet. A percent luminal area for each anastomosis was calculated relative to the mean tracheal area three rings above and three rings below the anastomosis. There was little difference between interrupted and continuous technique with either suture material (p = 0.94). In 10 animals that each served as its own control for suture material, PDS anastomotic area was 55.0% +/- 4.1% of mean tracheal luminal area compared with 45.4% +/- 7.1% for Vicryl anastomoses (p = 0.06). Histologic analysis revealed a more intense inflammatory reaction surrounding multifilament Vicryl sutures with more rapid resorption and greater subsequent fibrosis relative to the reaction seen with PDS sutures. A small clinical experience with seven infants has confirmed short-term satisfactory clinical performance of continuous PDS suture for tracheal anastomosis.