Objective: In recent years, much attention focused on improvement of implantation rate in ART cycles. Human in vitro fertilization and embryo transfer (IVF/ET) is accompanied by a low implantation rate even after a very successful IVF procedure. The mechanism of human embryo implantation is poorly understood and the causes of many implantation failures are not known. It is evident that molecular interactions at the embryo maternal interface at the time of implantation are crucial and inflammatory cytokines and growth factors are possibly involved in this process. The aim of our study was to analyze the effectiveness of endometrial biopsy, in increasing the rate of implantation and pregnancy in ART cycles. Materials and Methods: In prospective clinical trail study in Hamedan IVF centre sixty patients who candidate for IVF/ICSI cycle were divided in two equal groups, in case group (no=30) A single endometrial biopsy was performed using a Novak catheter on luteal phase of the cycle prior to ART cycles. Data are shown as mean-SD and comparison of variables were done using SPSS, t-test and chi-squre. Results: The comparison of characteristics of the study patients are shown in table 1. Conclusion: These data suggest that endometrial biopsy significantly increases the endometrial thickness. Implantation and pregnancy rates in ART cycles increased when endometrial thickness increased. Several mechanisms are thought to be involved in improving implantation including secretion of inflammatory cytokines and growth factors. Study of a larger group of patients is needed to confirm.