BACKGROUND AND STUDY AIMS: The advantages of a hybrid natural orifice transluminal endoscopic surgery approach to Roux-en-Y gastric bypass (hNOTES-RYGBP) might include: easier access to the peritoneal cavity, reduced number of ports and related complications, improved cosmesis, and others. However, currently available conventional endoscopic and laparoscopic instruments might be unsuitable for complex surgical procedures using transluminal access. The aim of this study was to investigate the feasibility and limitations of a NOTES RYGBP. METHODS: hNOTES-RYGBP was performed in human cadavers. Pouch creation was achieved by needle-knife dissection using a transvaginal, flexible scope. Articulating linear staplers were placed transumbilically to transect the stomach. Measurements of the small bowel were accomplished intraluminally or with flexible and rigid graspers. New methods were tested to create the gastro-jejunal anastomosis. A linear laparoscopic stapler was used to form the jejuno-jejunal anastomosis. RESULTS: Stapler manipulation and anvil docking, bowel manipulation and measurement, and tissue dissection presented the main obstacles for hNOTES-RYGBP. Conventional instruments were too short for some transvaginal manipulations. The time to complete the procedure was 6 - 9 hours. It was feasible to perform a complete hNOTES-RYGBP in four out of seven cadavers. Two cadavers were unsuitable due to anatomical abnormalities or advanced decay. One procedure was terminated before completion because of time constraints. Combinations of flexible and rigid visualization and manipulation were helpful, especially for dissection and gastric pouch creation. CONCLUSIONS: Several factors made hNOTES-RYGBP very challenging and time-consuming. A lack of proper instrumentation resulting in insufficient tissue traction, countertraction, and instrument manipulation complicated several steps during the procedure. A combination of flexible with rigid endoscopic techniques offers specific advantages for components of this type of surgery. Changes in instrument design are required to improve more complex endosurgical procedures.