Background: Endometrial thickness (ET) is one of the best predictors of implantation rate and continued success rate for pregnancy. There were possible beneficial effects of sildenafil citrate or estradiol on endometrial receptivity. The aim of this study was to compare the effect of Vaginal Sildenafil versus Oral Estradiol Valerate on Endometrial Thickness and Pregnancy Rate in infertile women undergoing induction of ovulation by clomiphen citrate. Patients and Methods: This Randomized control study was conducted on 44 infertile women undergoing induction by Clomiphen Citrate attending infertility and