To evaluate the hormonal effect of laparoscopic ovarian punch resection in polycystic ovary syndrome (PCO), seven PCO patients were examined for pulsatile gonadotropin secretions and pituitary sensitivity before and after operation. Marked reductions of luteinizing hormone (LH) pulse amplitudes, mean LH levels, pituitary LH responsiveness, and circulating androgen levels (P less than 0.05) were observed, 3 to 4 days and 6 weeks postoperatively. LH pulse frequency, follicle-stimulating hormone (FSH), and prolactin (PRL) did not change significantly. These results are consistent with the reported hormonal effects of wedge resection and suggest that the impairment of ovarian surface acts on the hypothalamo-pituitary axis to decrease pituitary hypersensitivity and the key factor behind the resultant hormonal change lies not deep inside the ovarian stroma but in the superficial ovarian capsule.