Introduction and Objective: Polycystic ovary syndrome (PCOS) is one of the causes of infertility due to the lack of chronic ovulation. Meanwhile, administration of human chorionic gonadotrophin (HCG) and possibility oxytocin is a method of trigger of ovulation. The present study aimed to investigate theeffect of oxytocin and HCG on ovulation in patients with clomiphene citrate-resistant PCOS. Materials and Methods: This is a double-blind clinical trial performed on 126 patients with clomiphene citrate-resistant PCOS, in Shahid Akbar-Abadi Hospital in Tehran. Ovulation stimulation was performed with (Letrozol 5mg + 10 units of oxytocin),(5,000 units of HCG +Letrozol 5 mg), and(HCG plus oxytocin+5 mg Letrozol). Then information including personal characteristics, contact number, clinic file number, gravidity, parity, history of abortion and previous illness, history of specific drug use, follicle count, dominant follicle size, ovulation symptoms in ultrasound, serum progesterone in luteal phase, and pregnancy outcome were evaluated and recorded in each of the three groups and the results were compared. Findings: Overall, 20% of patients responded to the treatments without any side effect and became pregnant. There was no significant difference in pregnancy rate of infertile women in different groups. In addition, the dominant follicle size and folliclecount in infertile women were studied, and there was no significant difference between the groups ( p -values 0.8 and 0.59, respectively). Of the 91 non-pregnant patients, ovulation induction occurred in 36 women (39.5%) in the next cycles of whom 8 (22.2%) were in the oxytocin group, 10 (27.8%) in the HCG group, and 18 (50.0%) in the oxytocin plus HCG group. Of these 36 patients, 10 (27.8%) were re-induced for ovulation in subsequent cycles of whom 2 (20.0%) were in the oxytocin group, 5 (50.0%) in the HCG group, and 3 (30.0%) in the oxytocin plus HCG group. There was no significant difference in mean endometrial thickness of infertile women treated in different groups ( p =0.1).Comparison of patients in terms of abortion rate showed that among 24 pregnant women, 21 (87.5%) had no abortion and 3 (12.5%) had. Of the 3 cases of abortion, 1 was in the oxytocin group and 2 werein the HCG group. In addition, comparing patients in terms of multiplepregnancy showed 2 cases of twin pregnancy, of which 1 occurred spontaneously 6 months after treatment in the oxytocin plus HCG group,and the second case was in the oxytocin group. In total, 1 out of 24 pregnancies (4.2%) were twin. Finally, there was no statistically significant difference between the three groups in terms of the mean serum progesterone ( p =0.2). Conclusion: Since there was no difference in the fertility rate in threegroups ((Letrozol 5mg + 10 units of oxytocin), (5,000 units of HCG +Letrozol 5 mg), and (HCG plus oxytocin+5 mg Letrozol) and given the low size of the study population, and considering the cost-effectiveness and the fewerside effects of oxytocin, this method(Use of oxytocin(seems effective for trigger of ovulation in clomiphene citrate-resistant PCOS patients.