Bardet-Biedl syndrome (BBS) is a rare genetic disorder characterized by a wide range of phenotypic variability and associated with the development of life-threatening obesity. Birth weight tends to be normal, but rapid weight gain begins after the first year, probably due to polyphagia rather than abnormalities in energy metabolism. A morbidly obese 16-year-old male patient with BBS was referred to our institution, after nonsurgical methods of weight control had failed, for surgical treatment of his obesity. His preoperative body mass index (BMI) was 52.28 kg/m(2) (height, 1.84 m; weight, 177 kg) and was above the 99th centile for age and gender. The patient underwent laparoscopic Roux-en-Y gastric bypass (RYGBP). The postoperative period was uneventful. Three and a half years after the operation, the patient's weight has decreased to 118 kg (BMI, 34.85 kg/m(2)), while significant improvement in his hypertension, hyperuricemia, and mobility has been noted. In our BBS patient, RYGBP proved to be safe and effective; nevertheless, longer follow-up is required to evaluate the weight loss durability and to assess the lasting beneficial effect of surgical intervention on genetically determined co-morbidities.