BackgroundPolycystic ovary syndrome (PCOS) is the most prevalence endocrine disorder in the reproductive age of women. In these patients, medications such as clomiphene citrate, letrozole and metformin are used to induce ovulation and overcome infertility. AimsThis study was done for comparing the findings of Color Doppler sonography of the uterine and ovarian arteries in women with PCOS under treatment of two drug groups of letrozole-metformin and clomiphene-metformin. MethodsIntervention-applied study was performed on 108 women with secondary infertility due to PCOS in Imam Reza Hospital of Kermanshah in 2016. Women were divided in two groups of 54 people, for investigating the effect of letrozole-metformin and clomiphene-metformin on ovarian and uterine arteries. ResultsBlood flow in the uterus and ovaries significantly increased after treatment with letrozole-metformin and clomiphenemetformin (P<0.05). However, the effect of letrozolemetformin was significantly higher than that of clomiphenemetformin on uterine and ovarian arteries Resistance Index (RI) (P<0.05). ConclusionLetrozole-metformin as well as clomiphene-metformin have a significant effect on blood flow in the uterus and ovaries. The group which received letrozole-metformin had a better response in this regard. Key WordsInfertility, Resistance Index (RI), Polycystic Ovary Syndrome (PCOS) What this study adds:1. What is known about this subject? PCOD is one of the most common fertility disorders in women of reproductive age with several treatment methods. What new information is offered in this study?The reduction of RI in the uterine and ovarian arteries was greater in letrozole-metformin group compared to clomiphene citrate-metformin. Treatment with letrozolemetformin is recommended. What are the implications for research, policy, or practice?Since polycystic ovary can cause infertility, treatment or control of this disease can help infertile couples in fertility.