Objective: To assess the Prevalence of polycystic ovary syndrome (PCOS) in a cohort of young women with previous idiopathic central precocious puberty (ICPP) at least 3 years after menarche, and to look for any predictive factors of PCOS at the time ICPP was diagnosed. Design: Longitudinal study. Setting: Pediatrics unit, Verona, Italy. Patient(s): Forty-six young women (18.1 +/- 3.0 years) who had been treated with GnRH analogues during childhood, observed at gynecologic age of 6.23 +/- 3.3 years. Intervention(s): Semistructured interview concerning cycles, physical exam, blood sampling, and transabdominal pelvic ultrasound. Main Outcome Measure(s): Oligomenorrhea, LH, FSH, E-2, T, DHEAS, free T, delta4-androstenedione, 17-OHP, P, polycystic ovary morphology (PCOM). Result(s): Fifteen percent of the Young women had oligomenorrhea, 28% clinical hyperandrogenism, 48% biochemical hyperandrogenism, and 37% PCOM. A total of 32% of the patients had PCOS according to the Rotterdam definition and 30% had PCOS according to the Androgen Exess Society. The prevalent phenotype of PCOS was characterized by clinical and/or biochemical hyperandrogenism and PCOM. We did not find any predictive factors for PCOS at the time ICPP was diagnosed. Conclusion(s): Patients with ICCP are prone to developing PCOS. The prominent phenotype in this cohort was PCOM associated with clinical and/or biochemical hyperandrogenism. Further follow-ups of these young adult patients will clarify whether this phenotype persists and if it will have important long-term implications regarding increased risk of infertility or metabolic complications. (Fertil Steril (R) 2010;93:1185-91. (C)2010 by American Society for Reproductive Medicine.)