Prader-Willi syndrome (PWS) is the most common known genetic cause of life-threatening obesity in children. Organized in 1975 to provide a resource for education and information about Prader-Willi syndrome and support for families, professionals and other interested citizens, PWSA (USA) provides information, education, and support services to its members. PWSA offers a toll-free telephone number for information and referrals, a nationwide network of local chapters, parents, and professionals, and it funds research to expand knowledge and treatment options.