A case of intestinal evisceration through the anus due to spontaneous rupture of the rectosigmoid is reported. The patient was a 76-year-old widow with habitual constipation. The episode of evisceration occurred during effort. Emergency laparotomy was carried out and a 6-cm tear was found in the anterior wall of the rectum. No fecal soilage was observed in the peritoneal cavity. The laceration was closed in two layers. A colostomy was not performed. The postoperative course was satisfactory. Increased abdominal pressure may have been the cause of the rupture. Anemia and hypoproteinemia were observed in the patient. These may have been contributing factors.