In 1935, Stein and Leventhal first described the association between amenorrhea and polycystic ovaries, which we now know as polycystic ovary syndrome (PCOS). In fact, PCOS appears to be one of the more common endocrine disorders, affecting approximately 4% of reproductive-aged women. This disorder is also associated with an increased risk of insulin resistance and hyperinsulinemia, type II diabetes mellitus, dyslipidemia, endometrial carcinoma, and psychosocial dysfunction. An informal survey of conference participants indicated that for most women, the major criteria for PCOS “included (in order of importance): (i) hyperandrogenism and/or hyperandrogenemia, (ii) oligo-ovulation, [and] (iii) exclusion of other known disorders, such as Cushing’s syndrome, hyperprolactinemia, or congenital [non-classic] adrenal hyperplasia.” The presence of “polycystic ovaries on ultrasound” was also noted as a possible inclusion criterion, although this was felt to be particularly controversial. In general, PCOS can be viewed as a heterogeneous disorder in which ovarian, and possibly adrenal, androgen excess is present, along with varying degrees of gonadotropic and metabolic abnormalities. We should, however, note that PCOS is a diagnosis of exclusion in which other causes of oligoovulation or hyperandrogenism are ruled out by the examining clinician.