Background and study aims: Laparoscopic gastric bypass is a recently introduced treatment option for morbid obesity, with promising initial results. Stenosis of the gastroenterostomy is a recognized complication. The efficacy and safety of endoscopic balloon dilation for the management of this type of anastomotic stenosis has not been studied. Patients and methods: 450 patients who underwent laparoscopic gastric bypass at our institution were followed prospectively. All patients had a 15 ml gastric pouch and either a 75 cm or 150 cm jejunal Roux limb depending on whether obesity was morbid (body mass index (BMI) < 50kg/m2) or super-morbid (BMI > 50kg/m2). Patients who developed symptoms compatible with stenosis of the gastrojejunostomy were referred for upper gastrointestinal endoscopy. Results: 14 patients, 11 women and three men, underwent a total of 27 endoscopies, with 23 balloon dilations. Their average age was 46 years (range 33-59 years), average preoperative BMI was 47 kg/m2, and they presented an average of 2.7 months after surgery (range 0.3-15.7 months). Of the 14 patients, 13 had a stricture of the gastrojejunostomy and one patient had edema. For initial dilation, a 15 mm hydrostatic balloon was used in 12 patients and an 18 mm balloon in two patients. There was response to treatment with the 15 mm balloon in seven of the 12 patients (58%), and they required no further dilation; in one there was a response to a further 15 mm balloon dilation; in three patients a response to subsequent 18 mm balloon dilation; and one patient required 18 mm and 25 mm balloon dilations. The two patients treated with an initial 18 mm balloon dilation required no further dilations. The average length of follow-up after successful dilation was 18 months (range 7-30 months). There were no complications with any of the 23 dilations performed. Conclusion: Stenosis of the gastroenterostomy after laparoscopic gastric bypass occurred in 3.1 % of the patients in this series. It can be successfully and safely treated with endoscopic balloon dilation with good long-term follow-up.