Excessive adrenal androgen production contributes to hyperandrogenism in polycystic ovarian disease (PCO). This study was performed to determine the concentration of basal plasma ACTH in PCO patients and normal women and correlate its level with that of circulating adrenal androgen. In PCO patients, significant increases in serum testosterone, androstenedione, and dehydroepiandrosterone sulfate were noted compared to levels in normal women. The mean circulating plasma ACTH in PCO patients (22 ± 2 pg/ml) was not different from that in normal controls (20 ± 2 pg/ml). The mean ratio of dehydroepiandrosterone sulfate to ACTH in individual PCO patients was significantly greater than that in normal subjects, whereas the cortisol to ACTH ratio was similar in both groups. These results suggest that increased adrenal androgen production in PCO patients is not due to abnormal ACTH secretion but arises from either altered adrenal responsiveness to ACTH or abnormal adrenal stimulation by a factor(s) other than ACTH. (J Clin Endocrinol Metab54: 1265, 1982)