The authors observed 105 cases of external intestinal fistula of various localization and found that the destruction of the intestinal wall under the conditions of suppurative peritonitis, together with the tampons and drainage tubes inserted into the abdominal cavity and left there for a long period of time, constitute the main causes of the occurrnce of intestinal fistula. Surgical treatment of a lip-shaped fistula (63 cases) of the small intestine and colon, mainly by the intraabdominal method, was carried out. Tubular fistula was closed conservatively in 22 cases. The intestinal motor activity was studied in 20 cases and potassium iodide resorption was investigated in the experiments on 20 animals. Some practically important recommendations are given.