Abstract: Objective To study the effects of met formin(Met)on endocrine metabolism and pregnancy outcom in patients with pcos and insulin resistance.Methods Sixty seven women with polycystic ovary syndrone(pcos)were studied.Body mass index(BMI),serumluteinizing hormone,follicle stmiulating hormone,estradiol,testo sterone,serumleptin,insulin releasing and oral glucose to lerance were measured.The patients with insulin resistance(IR)and pcos were divided into two groups randomly and were treated with Met,Diane 35,respectively for three months.The indicator measurements were perfomed again in two groups.Results Insulin resistance existed in 59.7% of pcos patients.The differences in fasting insulin(FINS),leptin and the ovulation rate between two groups were significant(P<0.05).The differences in pregnancy complications and delivery mode between pregnant women with pcos and insulin resistance and the natural conception group were significant(P<0.05).Conclusion Met can decrease the FINS and the rate of spon taneous abortion in early pregnancy.The threatened abortion and gestational diabetes is more likely to occur in pregnant women with pcos and insulin resist ance.The key is the use of insulin sensitizer to decrease the FINS.