Uterine cells carry out proliferation and differentiation for preparation the embryonic implantation during pregnancy. Therefore regulation of the cell proliferation is an essential step for uterine preparation, but there is not much information about the proliferation related genes in pregnant uterus. To identify these implantation specific genes, a PCR-select cDNA subtraction method was employed and got a few genes. One of the identified genes is a novel gene encoding oral tumor suppressor doc-1. To detect the doc-1 expression on the pregnant uterus, dot blotting, RT-PCR, and in situ hybridization were employed. Dot blotting revealed that doc-1 mRNA expression increase after implantation. During normal pregnancy, doc-1 mRNA expression was detected as early as day 1 of pregnancy with RT-PCR. Its expression was increased about 15 times after embryonic implantation. doc-1 transcript was localized in luminal epithelial cells but it was very faint during preimplantation. After starting the implantation, it localized in the stromal cells; heightened expression of doc-1 correlates with intense stromal cell proliferation surrounding the implanting blastocyst on day 6 morning. However in the decidualized cells, the intensity of localized doc-1 mRNA was weak. From those results, it is revealed that doc-1 express at pregnant uterus of the mouse. In addition it is suggested that doc-1 is the gene regulating the proliferation of the luminal epithelial cells and stromal cells during early implantation and decidualization.