Objective: For last 40 years, Clomiphene Citrate has been the first line treatment for anovulation in PCOS. But it has adverse anti-estrogenic effects on endometrial and cervical mucus that could prevent pregnancy in spite of successful ovulation. Letrozole (aromatase inhibitor) induces ovulation without antiestrogenic effects. This study compares efficacy of Letrozole versus Clomiphene as ovulation induction drug in PCOS patients.