A 16-year-old male adolescent diagnosed to have the Williams-Beuren syndrome was referred to our obesity outpatient clinic, due to his morbid obesity (body mass index 39.2 kilograms per square metre) and gluttony. After several unsuccessful dietary treatments, we started therapy with sibutramine. As growth hormone (GH) deficiency was diagnosed by an additional GH-stimulation test, we commenced with a GH-treatment.