Introduction: Polycystic ovarian syndrome (PCOS) is one of the most common endocrine disorders in women of reproductive age (6.8% -18%) and is one of the most common causes of infertility due to ovulation factors in 55-70% of infertile women. In this study, we compared clomiphene and letrozole in the induction of ovulation in patients with PCOS. Material & Method: This randomized clinical trial study included 80 infertile patients with PCOS. The patients were divided into two groups of 40, treated with letrozole or clomiphene citrate. In the clomiphene citrate group, two tablets 50 mg were taken daily and in the letrozole group, 2 tablets of 2.5 mg daily were prescribed on the third to seventh days of the cycle for 5 days. Results: In the clomiphene group, the cycle was compatible with PCOS in 30 patients (75%) and in the group receiving letrozole in 33 patients (82.5%). Hyperandrogenism consistent with PCOS in the clomiphene group was present in 25 patients (62.5%) and in the group receiving letrozole in 22 patients (55%). The evidence of PCOS-compatible ultrasonography was found in 31 patients (77.5%) in the clomiphene group and in 35 patients (87.5%) in the letrozole group. The frequency of pregnancy in the clomiphene group (45%) was lower than the letrozole group (50%).Conclusion: It seems that the efficacy and success rate of clomiphene and letrozole in the treatment of infertility due to ovulation failures are similar in patients with PCOS and both could increase ovulation and pregnancy rate. In other words, these two drugs are not superior to each other and can be selected according to the patient's tolerance, cost and side effects.
