Superior results in terms of the percentage of excess weight loss (%EWL) have been ascribed to the biliopancreatic diversion with duodenal switch (DS) compared to the Roux-en-Y gastric bypass (RGB), however prior studies were often not well controlled. This study compares similar weight patients undergoing either the DS or RGB. METHODS: A retrospective comparison of RGB and DS performed at a single center between 2/02-12/04 on patients of similar weight and BMI was done. Pre- and postoperative care was identical for all patients. RGB is performed with a 75cm biliopancreatic limb, a 100cm antecolic Roux limb, and a hand-sewn gastroenterostomy to a 20cc linear gastric pouch. DS is performed with a 250cm alimentary limb, a 100cm common channel, and a retrocolic hand-sewn duodenoenterostomy. RESULTS: Preoperative weight and BMI were similar in both groups. At 1 year postop, BMI was 28.0±4.6kg/m2 for RGB and 26.8 ±3.8kg/m2 for DS (p=NS), %EWL was 73.7±16.0% for RGB and 77.8±12.2% for DS (p=NS), and weight lost was 110±32lbs for RGB and 118±20lbs for DS (p<0.05). At 1 year postop, 4/66 (6.1%) RGB patients were still obese with a BMI >35, versus 2/30 (6.7%) DS patients (p=NS). CONCLUSIONS:Patients undergoing DS had similar outcome in terms of %EWL and weight lost compared to RGB patients, but DS had significantly higher rates of reoperation and complication.