PCOS affect approximately 6-10% of women of child bearing age. Insulin resistance & compensatory hyperinsulinemia play a central role in PCOS. It is characterized by chronic anovulation & infertility with either oligomennorhea or amenorrhoea & hyperandrogenism. The ovary does not make the hormones needed for the eggs to fully mature. Follicles may start to grow and build up fluid but none of the follicle becomes large enough. Instead some follicles may remain as cysts. Since no follicle becomes large enough and no egg matures or is released, ovulation does not occur and the hormone progesterone is not made. Without progesterone, a woman's menstrual cycle becomes irregular or ceases. The cysts so produced make male hormones, which also prevent ovulation. The action of stradiol on the hypothalamic pituitary axis and on the endometrium is unopposed because of a lack of cyclical progesterone secretion. Insulin sensitizers like metformin is thus a rationalized therapeutic approach for women having primary infertility due to PCOS. Metformin pecifically targets not only insulin resistance but several other aspects of the syndrome including reproductive abnormalities