Adrenal function may be abnormal in women with polycystic ovary syndrome (PCOS). This study aims to evaluate adrenal steroid response to the adrenocorticotropic hormone (ACTH) stimulation test and to find out the effect of high serum testosterone levels on adrenal response. We have also investigated any subtle enzyme deficiency by extending blood sampling to 2 h with 30 min intervals following ACTH administration. Twenty-eight women with PCOS and 18 healthy controls without hirsutism and oligomenorrhea were included in the study. After determining their serum basal levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, dehydroepiandrosterone sulfate (DHEAS), 17-hydroxyprogesterone (17-OHP), and progesterone, ACTH stimulation test was performed. The change in serum 17-OHP and the summed rate of change in serum 17-OHP and progesterone levels were estimated and 95th percentile for each value was computed. Women with PCOS were heavier and move hirsute than controls (p < 0.01, p < 0.001, respectively). Sevum basal LH, LH: FSH ratio, testosterone (p < 0.001, for all), DHEAS (p < 0.01), and 17-OHP (p < 0.05) were higher in women with PCOS. All of the 17-OHP measurements, including basal and each 30 min interval after the administration of ACTH, were higher in women with PCOS than those of healthy controls (p < 0.05, p < 0.002, p < 0.001, p < 0.015, p < 0.018, respectively). However, the incremental changes in serum 17-OHP30-0, 17-OHP60-0, 17-OHP90-0, 17-OHP120-0, and the summed rate of change in serum 17-OHP and progesterone in women with PCOS were not different from those in healthy controls. The incremental response in terms of serum progesterone, DHEAS, and testosterone levels to the ACTH stimulation test for each 30 min interval was not different in women with PCOS than in healthy controls. We were not able to show any critical value for serum basal testosterone and DHEAS levels that would effect response to ACTH stimulation in terms of 17-OHP levels. We have concluded that extending the duration of blood sampling up to 2h has no advantage in evaluating adrenal steroid response to ACTH stimulation. Since serum 17-OHP levels remain within normal limits in response to ACTH stimulation, the origin of elevated serum basal 17-OHP levels may be polycystic ovaries. Elevated serum testosterone level doer not have any adverse effect on adrenal function. Sevum progesterone measurement seems to have no place in the diagnosis of 21-hydroxylase deficiency. Adrenal androgenic response to ACTH stimulation is normal in women with PCOS.