Roux-en-Y gastric bypass (RYGB), mostly since it is performed laparoscopically, is presently the technique of choice for the treatment of morbid obesity. In the United States, more than 80% of all bariatric procedures are RYGB, and our country follows the same way with more than 60% of RYGB in 2004. In Switzerland, this procedure can be considered for morbidly obese patients only (Body Mass Index > or = 40 kg/m2). RYGB is both strongly restrictive and lightly malabsorptive, and induces a 60% mean excess weight loss with a dramatic resolution of comorbidities. The mortality and morbidity of this operation are very low, particularly when compared to the death and disease risks associated with obesity. These patients should be treated by a specialized multidisciplinary team.