The authors present the case of a 43-year-old women who underwent a laparoscopic gastric bypass in 2003 for morbid obesity. They report that 2 years later, she had maintained significant weight loss, but had developed acute abdominal pain, followed by nausea and emesis. In the emergency room, she had diffuse tenderness, tachycardia, and leukocytosis. After initial resuscitation, a computed tomography was performed, which showed free air above the liver and thickened small bowel loops. She was brought emergently to the operating room for laparoscopy. At surgery, turbid fluid and inflamed small bowel loops were seen. A perforated marginal ulcer was discovered in the Roux limb, approximately 2 cm distal to the gastrojejunal anastomosis. The perforation was oversewn primarily and patched with omentum. The repair was tested by intraoperative endoscopy. A gastrostomy tube also was placed within the gastric remnant for enteral access. The patient did extremely well postoperatively, and had an uneventful postoperative course. She was discharged on postoperative day 4. The gastrostomy tube was removed at 1 month, and at this writing, she remains well since surgery. An upper endoscopy at 2 months was completely normal, and the Helicobacter pylori test results were negative. The gastric pouch had not significantly enlarged since initial surgery, as indicated by both endoscopy and barium study. Marginal ulcer is reported to be 0.6% to 16% after laparoscopic gastric bypass. Etiologies include gastrogastric fistula, excessively large gastric pouch containing antral mucosa, H. pylori infection, nonsteroidal antiinflammatory use, and smoking. Unfortunately, none of these applied to the reported patient. Because her exact etiology remains unknown, she at this writing continues to receive proton pump inhibitor therapy.