BACKGROUND One-Anastomosis Gastric Bypass (OAGB) by laparoscopy consists of constructing a divided 25-ml (estimated) gastric pouch between the esophago-gastric junction and the crow's foot level, parallel to the lesser curvature, which is anastomosed latero-laterally to a jejunal loop 200 cm distal to the ligament of Treitz. METHODS The results of our first 209 OAGB patients operated from July 2002 to June 2004 are reported. Mean age was 41 years (14-66), BMI 48 (39-86) and mean excess body weight 66 kg (35-220). In 144 patients, OAGB was the only operation performed, and in 61 patients it was accompanied by other surgery (18 cholecystectomies, 5 incisional hernia repairs, and 38 adhesiolysis), and in 4 patients a restrictive bariatric operation had been performed previously. RESULTS 2 patients (0.9%) were converted to open surgery due to uncontrollable bleeding. 3 patients (1.4%) needed re-operation in the immediate postoperative period. 5 patients (2.3%) needed prolonged hospital stay due to acute pancreatitis in 1 and anastomotic leakage in 4, all resolving with conservative treatment. 2 patients died (0.9%), 1 from fulminant pulmonary thromboembolism and 1 from nosocomial pneumonia. Long-term complications have occurred in only 2 patients who developed clinically significant iron-deficiency anemia. Mean excess weight loss was 75% after 1 year and >80% at 2 years. CONCLUSION OAGB is a simple, safe and effective operation with less perioperative risk than conventional gastric bypass, quicker return to normal activities, and better quality of life.