The polycystic ovary syndrome has a pubertal onset, with menstrual cycle irregularities and infertility in adulthood, as well as general health hazards such as increased risk for diabetes mellitus and myocardial infarction. Thus, prevention would be important. But as specific etiological factors are not known, nor is specific intervention. In order to use long-term intervention programs in children and adolescents, particularly rigid criteria must be used regarding proven safety and efficacy. In obese subjects, weight loss is very important, having beneficial effects on most aspects of the syndrome, such as subjective symptoms, infertility, hyperinsulinemia and related metabolic aberrations, and long-term health risks. Well controlled, long-term follow-up studies are needed on the role of prepubertal hyperandrogenism, hyperinsulinemia, gonadotropins, and ovarian morphological aspects in the development of PCOS, and possibilities of prevention.