The polycystic ovary syndrome (PCOS) is one of the most common human endocrine abnormalities, affecting 4% to 6% of reproductive-aged women. Although patients with PCOS primarily demonstrate excess production of ovarian androgens, elevated adrenal androgen (AA) levels, primarily dehydroepiandrosterone sulfate (DHEAS), are observed in 20 to 30% of patients if age-related normative values are used. Adrenal androgens may contribute to the phenotype of PCOS, including the development of hirsutism. Overall the cause(s) of the excess AAs levels in PCOS remains unclear. Adrenal androgen levels in PCOS appear to be determined, at least in part, by extra-adrenal factors such as ovarian steroids and insulin. Nonetheless, the primary effect of extra-adrenal androgens and insulin appears to be increased sulfotransferase activity, augmenting the conversion of DHEA to DHEAS. In fact most studies have demonstrated a limited role for extra-adrenal factors in the regulation of circulating AA levels in vivo. Primarily, AAs and AA excess in PCOS (and in normal subjects) appear to be under significant genetic control. Hence, it is possible that AA excess in PCOS may reflect an inherited abnormality of steroidogenesis. However, and consistent with the significant degree of populational heterogeneity observe in AA levels and secretion, it is more probable that the elevated AA levels found in patients with PCOS may actually reflect selection bias, with a disproportionate number of the women with the highest levels of AAs also having the greatest prevalence of PCOS. In essence, elevated AA secretion in women may reflect an exaggerated AA secretion in response to adrenocorticotrophic hormone (ACTH) stimulation, and may be a predisposing risk factor for the development of PCOS. © 2002 Lippincott Williams & Wilkins, Inc.