Excess ovarian androgen production might be a cause of the polycystic ovary syndrome (PCO). Previous studies have evaluated adult women with long-standing abnormality of the hypothalamic-pituitary gonadal axis. Abnormal ovarian function in such patients could be a primary or even a secondary finding. For that reason, this study was designed to evaluate ovarian androgen production in symptomatic adolescent females. Simultaneous adrenal suppression, by using dexamethasone, and ovarian stimulation, by using gonadotropin-releasing hormone (GnRH), were achieved in 12 patients. Following stimulation, blood was serially obtained over 8 hr to measure gonadotropin, estrogen, and androgen responses. Based on the androgen response, patients could be divided into two groups. Group A (five) had a significant increase (p less than 0.01) in free testosterone, whereas group B (seven) had no increase in any androgen, including free testosterone (significantly different from group A, p = 0.01). All patients in group A had enlarged or cystic ovaries, whereas only one-quarter patients in group B had enlarged ovaries (significantly different from group A, p less than 0.03). The pituitary and estrogenic response was similar in both groups. These preliminary data suggest that some patients with PCO (group A) have a primary abnormality in ovarian androgen production early in the course of their disease.