The present study was design to compare letrozole (5 mg) and clomiphene citrate (100 mg) as first line ovulation induction drug in infertile anovulatory polycystic ovarian syndrome (PCOS) women.Methods: This prospective randomized clinical trial included 60 cases of PCOS with anovulatory infertility. The first group comprised of 30 patients who received 5 mg letrozole daily and the second group received 100 mg clomiphene citrate daily for 5 days starting on day 2-5 of menses. Both the groups

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... e followed by ultrasound for follicle monitoring, ovulation and endometrial thickness. When dominant follicle reaches a diameter of more than or equal to 18mm and endometrial thickness ≥7.5 mm, human chorionic gonadotrophin (hCG) 5,000 IU was given intramuscularly and timed intercourse was advised. Main outcome measures were occurrence of ovulation, endometrial thickness and pregnancy rates.Results: The mean age, body mass index, and number of cases of primary and secondary infertility in both the groups showed no statistically significant difference. Multi-follicular development during induction was statistically significantly greater in the clomiphene group (1.27±1.11 versus 2.03±1.65; p=0.041). Ovulation occurred in 24 subjects (80%) in letrozole group and 18 subjects (60%) in the clomiphene group, with a statistically significant difference between the two groups (p=0.024). Pregnancy occurred in 16 subjects (53.33%) in letrozole group and 7 subjects (23.33%) in clomiphene group, which shows statistically significant difference between the two groups (p=0.048).Conclusions: Though number of developing follicles was found statistically significant with clomiphene citrate but ovulation rate and pregnancy rate were higher with letrozole group. Therefore, letrozole is a safe and better alternative for ovulation induction in patients of anovulatory PCOS, and it may be considered as a first line treatment for ovulation induction in these patients.