In this article the authors discuss the genetic, medical, and endocrinologic issues of Prader-Willi syndrome and their treatment. The authors also present the typical cognitive profile characterized by specific strengths and areas of disability. The behavioral phenotype of Prader-Willi syndrome affects four domains: food-seeking related behaviors; traits that indicate lack of flexibility; oppositional behaviors, and interpersonal problems. The management of the maladaptive behaviors is challenging and requires lifelong restrictive supervision (to prevent morbid obesity), addressing psychiatric comorbidity, psychopharmacologic management exacerbated by metabolic abnormalities, ongoing medical care, and, in many cases, institutional treatment. The multiple facets of the clinical problems demand a multidisciplinary approach with anticipatory medical and psychiatric care, oriented to enhancing the quality of life of individuals who have Prader-Willi syndrome.