In this study, real-time PCR and immunohistochemistry were used to detect coxsakie and adenovirus receptor (CAR) expression. Both localization and quantity were evaluated in the uteri obtained at days post coitus (dpc) 2.5, 4.5, 6.5, 8.5. Outcome of PCR was assessed by 2(-Delta Delta Ct) method. Image Pro-Plus 6.0 software was used for quantifying mean density of CAR expression in immunohistochemical sections. We found relatively weak CAR expression in the mouse uteri during implantation window. PCR and immunohistochemistry revealed highest CAR expression was detected on dpc 2.5 followed by down-regulation of CAR at dpc 4.5 and 6.5 (with significant difference). At dpc 8.5, CAR expression was increased slightly again. It is concluded that during implantation, the expression of CAR mRNA and protein is declined, resulting in the impairment of tight junction between cavity epithelium cells. After implantation window closure, CAR appears again to maintain epithelium stability. CAR might play an important role during embryo implantation procedure.