The mechanism of marginal ulceration after laparoscopic gastric bypass surgery is poorly understood. We reviewed the incidence, presentation, and outcome of ulcer disease in consecutive patients undergoing laparoscopic gastric bypass surgery.The outcomes of 201 consecutive laparoscopic gastric bypass surgery procedures were prospectively analyzed for complications. All procedures were performed using a linear stapled anastomosis and absorbable suture.The incidence of marginal ulcer disease was 3.5% (7 patients). One patient, the only smoker, presented with an acute perforation 4 months postoperatively. Three other patients presented with bleeding-all required transfusion. The remaining 3 patients presented with severe pain. At endoscopy, all patients had ulcerations associated with the Roux limb mucosa and were all successfully treated using proton pump inhibitors and sucralfate therapy. Symptoms of marginal ulceration occurred an average of 7.4 months (range 3-14) after surgery. The average follow-up was 19.8 months. No preoperative factors were predictors of ulcer disease, including body mass index, age, gender, or co-morbidities.Marginal ulcers using the linear-stapled technique occurred in 3.5% of patients. Three distinct clinical presentations occurred: bleeding, pain, or perforation. No preoperative risk factors were identified that predicted for this complication. Medical management is an effective treatment.