Recent progress in the diagnosis, pathophysiology, long-term ramifications and treatment of polycystic ovary syndrome has been rapid but the pathogenesis remains a challenging enigma and the treatment symptomatic. Objective ultrasound criteria for diagnosis are being formulated and have enabled an appreciation of the true prevalence and the associated clinical and biochemical manifestations. Although a heterogeneous syndrome, the final common pathway seems to involve a dysregulation of enzymes responsible for ovarian androgen biosynthesis, possibly influenced by insulin, growth factors and luteinizing hormone. A single gene defect, inherited in an autosomal dominant pattern, has been proposed. The treatment is necessarily symptomatic, depending on the needs of the patient. Long-term deleterious sequelae now emerging may demand suppression of the syndrome earlier in life. As the most prevalent cause of anovulatory infertility, a further elucidation of the basic pathogenesis is needed to allow the application of more specific and successful modalities of treatment.