The final frontier in endoscopy is the peritoneal cavity which was recently reached through natural orifice transluminal endoscopic surgery (NOTES). Endoscopic perforation caused by NOTES has been the major challenge for this procedure because of the risk of peritonitis and consequent complications. We describe in a dog model the use of an overtube system, one of them with a balloon, to access the peritoneal cavity by NOTES. It permits direct access to the peritoneal cavity from the mouth and also allows the performance of a controlled perforation and provides conditions for a safe closure of the gastric wall.