Objective: We tested the hypothesis that the three clinical phenotypes of polycystic ovary syndrome (PCOS) represent forms of the same metabolic disorder. Design: Prospective cohort analysis. Setting: University- based tertiary care. Patient(s): Three- hundred sixteen untreated consecutive women diagnosed as having PCOS. Intervention(s): None. Main Outcome Measure(s): Each subject underwent an evaluation of ovulatory function, body habitus, acne, and hirsutism; serum free and total testosterone (T), 17- hydroxyprogesterone (17- HP), and DHEAS; and fasting plasma glucose and insulin levels. Insulin resistance and β - cell function were assessed using the homeostatic assessment model equation (HOMA- IR and HOMA- β - cell, respectively). Result(s): The Oligo+ HA+ Hirsutism phenotype was present in 48% of subjects, Oligo+ HA in 29% , and Oligo+ Hirsutism in 23% . The three phenotypes did not differ in mean body mass index, waist- to- hip ratio, racial composition, degree of oligo- ovulation, prevalence of acne, or family history of hyperandrogenic symptomatology. However, subjects demonstrating the Oligo+ HA+ Hirsutism phenotype were the youngest and had the greatest degrees of hyperandrogenemia, hyperinsulinemia, and β - cell function; patients with the Oligo+ Hirsutism phenotype where the oldest and had the mildest degrees of hyperandrogenemia, hyperinsulinemia, and β - cell function. Subjects with the Oligo+ HA phenotype demonstrated intermediate degrees of hyperandrogenemia and metabolic dysfunction. Conclusion(s): We conclude that the three clinical phenotypes of PCOS do not represent forms of the same metabolic disorder and may be the result of varying degrees of metabolic dysfunction; greater degrees of β - cell function and circulating insulin levels favored the development of hirsutism and frank hyperandrogenemia. Objective: We tested the hypothesis that the three clinical phenotypes of polycystic ovary syndrome (PCOS) represent forms of the same metabolic disorder. Design: Prospective cohort analysis. Setting: University- based tertiary care. Patient (s): Three- hundred sixteen untreated Interventions (s): None. Main Outcome Measure (s): Each subject underwent an evaluation of ovulatory function, body habitus, acne, and hirsutism; serum free and total testosterone (T), 17- hydroxyprogesterone (17-HP), and DHEAS; and fasting plasma glucose and insulin levels. Insulin resistance and β-cell function were assessed using the homeostatic assessment equation equation (HOMA- IR and HOMA- β- cell, respectively) : The Oligo + HA + Hirsutism phenotype was present in 48% of subjects, Oligo + HA in 29%, and Oligo + Hirsutism in 23%. The three phenotypes did not differ in mean body mass index, waist-to- hip ratio, racial composition, degree of oligo-ovulat However, subjects demonstrating the youigo and HA the Hirsutism phenotype were the youngest and had the greatest degrees of hyperandrogenemia, hyperinsulinemia, and β-cell function; patients with the Oligo + Hirsutism phenotype where the oldest Conclusion with the Oligo + HA phenotype demonstrated intermediate degrees of hyperandrogenemia and metabolic dysfunction. Conclusion (s): We conclude that the three clinical phenotypes of PCOS do not represent forms of the same metabolic disorder and may be the result of varying degrees of metabolic dysfunction; greater degrees of β - cell function and circulating insulin levels favored the development of hirsutism and frank hyperandrogenemia.