First described in 1956, Prader-Willi syndrome (PWS) is a multi-systemic disorder that results in obesity, short stature, hypogonadism, and behavior problems. Recently awareness of the hormonal components of the syndrome has increased and researchers have posited that insights into the pathophysiology of the syndrome and its relation to energy regulation will provide greater understanding of the causes of normal obesity.Eiholzer and l'Allemand (both of Foundation Growth Puberty Adolescence, Switzerland), along with Zipf (pediatrics, Ohio State U., US), present 17 papers from an October 2002 conference devoted to the topic. Broad topics discussed include the central nervous system and body weight homeostasis, energy balance in PWS compared to simple obesity, comorbidities of obesity, and treatment approaches.