The use of free peritoneal patch was evaluated for the effect on protection against intestinal anastomotic leakage in dogs. Free peritoneal patch was found to be effective in preventing the anastomotic leakage of the alimentary tract in borderline situation. Free peritoneal patch was more effective when applied with the 'smooth side out' than with the "smooth side in'. The usefulness of free peritoneal patch was also demonstrated in the treatment of the already established fistula of the cervical esophagus.