Objective To assess the effectiveness of transvaginal, ultrasoundguided, ovarian, interstitial laser coagulation treatment in anovulatory women with polycystic ovary syndrome (PCOS).Design A pilot study.Setting Assisted reproductive technology unit.Sample Twenty-three anovulatory women with clomifenecitrate-resistant PCOS.Methods Ultrasound-guided, transvaginal, ovarian, interstitial yttrium-aluminium-garnet laser treatment.Main outcome measures Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, prolactin and estradiol levels, spontaneous ovulation rate and pregnancy rate were measured over 6 months of follow up.Results Regular ovulation occurred in 19 out of 22 (86.4%) women in the 6 months following ovarian treatment (one woman was lost to follow up). On the postoperative second, fourth and sixth month, the mean serum LH levels were 4.54 SD 1.21 iu/l, 4.90 SD 2.18 iu/l and 4.42 SD 1.03 iu/l, significantly (P < 0.001, P < 0.001, P < 0.001) lower than the preoperative level of 13.89 ± 3.62 iu/l; the mean serum testosterone levels were 2.69 SD 1.83 nmol/l, 2.42 SD 1.11 nmol/l and 2.28 SD 1.96 nmol/l and significantly (P < 0.001, P < 0.001, P < 0.001) lower than the preoperative baseline value of 5.37 SD 3.09 nmol/l; the mean LH/FSH ratios of 0.93 SD 0.26, 0.88 SD 0.17 and 0.81 SD 0.14 were also significantly lower than the preoperative value of 2.78 SD 1.21 (P < 0.001). Pregnancy occurred in eight women and there was a cumulative pregnancy rate at 6 months of 36% (8/22) among the subjects. There were no significant operative complications.Conclusion Ultrasound-guided, transvaginal, ovarian, interstitial laser treatment appears effective in improving hormonal profiles and inducing ovulation and successful pregnancy in women with clomifene-resistant PCOS.