Objective: To determine whether the ovary in¯uences adrenal androgen secretion in women with polycystic ovary syndrome (PCOS). Design: Six PCOS-affected patients with clomiphene resistance and gonadotrophin hyperresponsivity, and six controls with regular ovulatory cycles, matched for age and body mass index. Methods: Bilateral ovarian wedge resection was performed to induce ovulation surgically for these refractory women with PCOS. The adrenal androgen secretions were evaluated in PCOS patients before and again 6 months after this surgery, and in the controls, using an ACTH stimulation test (0.25 mg synthetic ACTH(1±24)). Results: Biochemically, basal levels and the maximum net increases (D) of 17-hydroxyprogesterone (17-OHP) and androstenedione, D17-OHP/Dprogesterone and Dandrostenedione/D17-OHP ratios in response to exogenous ACTH were signi®cantly higher in PCOS patients before operation than those of controls. This purely ovarian surgery in women with PCOS was found to signi®cantly reduce their basal androstenedione, testosterone and LH levels, insulin/glucose ratio, and post-corticotrophic D17-OHP, Dandrostenedione, D17-OHP/Dprogesterone and Dandrostenedione/D17-OHP, without obvious changes in FSH, oestradiol, sex hormone-binding globulin, Ddehydroepiandrosterone, Ddehydroepiandrosterone sulphate, Daldosterone and Dcortisol values. Conclusions: Ovarian hyperandrogenicity from polycystic ovary may contribute to the enhanced adrenal P450c17a activity and subsequent D 4 androgen reserve revealed by the pharmacological corticotrophin stimulation in our special PCOS cases.