Background: Infertility is customarily defined as the inability to conceive after 1 year of regular unprotected intercourse. The infertility evaluation is typically initiated after 1 year of trying to conceive, but in couples with advanced female age (> 35 years), most practitioners initiate diagnostic evaluation after an inability to conceive for 6 months. Aim of the Work: To assess endometrial receptivity in women with unexplained infertility using sub-endometrial vascular flow resistant index and endometrial leukemia inhibitory factor (LIF). Patients and Methods: This clinical controlled trial was conducted at Ain Shams University Maternity Hospital during the period from August 2014 to September 2017 on 140 patients divided into two equal groups: Group I (study group): women with unexplained infertility defined as inability to conceive inspite of regular marital life for at least 12 months. Group II (control group): matched women with infertility due to tubal factor, recruited from outpatient gynecology or infertility clinic at Ain Shams University Maternity Hospital. Results: A cutoff value for LIF staining score of ≤1 predicted unexplained infertility with a sensitivity of 73.33% and specificity of 70.67%; whereas a cutoff of > 0.71 for subendometrial blood flow RI predicted unexplained infertility with a sensitivity of 70.67% and specificity of 86.67%. A cutoff of ≤10 mm for endometrial thickness had the highest sensitivity of 100%, but lacked specificity (only 16%). Conclusion: Leukemia inhibitory factor may be a predictor for unreceptive endometrium in cases of unexplained infertility. Subendometrial blood flow RI and endometrial thickness may be used rather than LIF IHC (due to its invasive nature)for the prediction of endometrial factor status in cases of unexplained infertility because of the statistically significant negative correlation between the above parameters. Recommendations: Further studies are needed to evaluate the predictive value of the multiple logistic model including (endometrial thickness, subendometrial blood flow color Doppler and LIF IHC score and even other proposed cytokines as VEGF, IL6 and integrins) in unexplained infertility.