Suture-holding capacity (breaking strength) of small bowel anastomoses made with interrupted or continuous sutures was assessed in two groups of rats. The tightness of the suture line was varied in a standardized manner in both groups. All types of anastomoses had similar strength immediately after surgery. After 72 h, suture-holding capacity had decreased by 50–55% (p 0.05) if sutures were loose. Changes in strength were similar regardless of whether interrupted or continuous sutures were used. Myeloperoxidase activity, reflecting tissue neutrophil accumulation, and hydroxyproline content were similar in all types of anastomoses after 72 h. Deterioration of early anastomotic strength is probably due to proteinase-mediated tissue degradation. It is speculated that tight sutures encourage proteolytic enzyme activity in the bowel wall by disturbing the local proteinase/proteinase inhibitor bala