Abstract: The polycystic ovary syndrome (PCOs) affects 5-10% of reproductive age women and it is the most common cause of unovulatory infertility. The aim of this clinical trial was to compare the combination therapy of letrozole and clomiphene with letrozole and tamoxifen as an infertility treatment in women with the polycystic ovary syndrome. In this study 9 infertile women between 18-40 years with the polycystic ovary syndrome who had no major medical disorders enrolled in this clinical trial. Patients were randomized in to 2 groups: one group was treated with Clomiphene Citrate (CC) 50 mg twice daily and letrozole 2.5 mg twice daily for 5 days (from day 3-7 of menstrual cycle) and group 2 took tamoxifen 10 mg twice daily and letrozole 2.5 mg twice daily for 5 days (from day 3-7 of menstrual cycle). Trans vaginal ultrasonography (TVS) was performed at the day 7 in order to determine number of follicles, size of follicles and Endometrial Thickness (ET). Pregnancy rate in the group of women who received tamoxifen and letrozole (Group B) was more than women who received CC and letrozole (Group A) (2.2% in group A vs. 17.8% in group B) that there is significant difference between two groups (p = 0.01). There is no significant association between two groups in incidence of OHSS, endometrial thickness and follicular size. It suggested co-administration of letrozole and tamoxifen was more effective due to low cost, low complication and greater access as an infertility treatment.