The effect of rosiglitazone on endocrine, metabolism and ovulatory performance in the paitents with polycystic ovary syndrome(PCOS) and insulin resistance was investigated. Twenty-five patients diagnosed as having polycystic ovary syndrome (PCOS) combined with insulin resistance were treated with rosiglitazone for 12 weeks. Before and after treatment, serum luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2), testosterone (T), androstenedione (A), sex hormone binding globulin (SHBG), insulin and glucose concentration, total cholesterol, triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholestero (LDL-C), apolipoprotein A, apolipoprotein B levels and ovulatory performance were determined. The results showed that after treatment serum insulin levels was decreased significantly (P<0.01). The HDL-C was increased while LDL-C decreased significantly (P<0.05, P<0.01). The serum LH, T, A concentrations and the ratio of LH/FSH were decreased, while SHBG levels increased significantly (P<0.01). The ovulation rate during clomiphene citrate therapy was 72 %, significantly higher than that before treatment. It is likely that reduction of hyperinsulinemia that is produce by rosiglitazone may effectively improve the endocrine, metabolism and ovulatory performance in the patients with PCOS and insulin resistance.