Object: The present study was accomplished to obtain a gene expression profile of the luminal epithelium during embryo apposition in comparison of implantation (1M) and interimplantation (INTER) sites. Material and Method: The mouse uterine luminal epithelium from IM and INTER sites were sampled on day 4.5 (Day of vaginal plug = day 0.5) by Laser Captured Microdissection (LCM). RNA was extracted from LCM captured epithelium, amplified, labeled and hybridized to microarrays. Results from microarray hybridization were analyzed by Significance Analysis of Microarrays (SAM) method. Differential expression of some genes was confirmed by LCM followed by RT-PCR. Results: Comparison of IM and INTER sites by SAM identified 73 genes most highly ranked at IM, while 13 genes at the INTER sites, within the estimated false discovery rate (FDR) of 0.163. Among 73 genes at IM, 20 were EST/unknown function, and the remain 53 were categorized to the structural, cell cycle, gene/protein expression, immune reaction, invasion, metabolism, oxidative stress, and signal transduction. Of the 24 structural genes, 14 were related especially to extracellular matrix and tissue remodeling. Meanwhile, among 13 genes up-regulated at INTER, 8 genes were EST/unknown function, and the rest 5 were related to metabolism, signal transduction, and gene/protein expression. Among these 58 (53+5) genes with known functions, 13 genes (22.4%) were related with $Ca^{2+}$ for their function. Conclusions: Results of the present study suggest that 1) active tissue remodeling is occurring at the IM sites during embryo apposition, 2) the INTER sites are relatively quiescent than IM sites, and 3) the $Ca^{2+}$ may be a crucial for apposition. Search for human homologue of those genes expressed in the mouse luminal epithelium during apposition will help to understand the implantation process and/or implantation failure in humans.