Implantation is thought to be interactive and synchronized process between mother and embryo, however, the mechanisms of the early implantation process remain unelucidated. Therefore, the effectiveness of in vitro fertilization and embryo transfer is still poor. As a result; immunohistochemically, type IV collagen and other extracellular matrix components were detected mainly below the epithelial layer. Type I and III collagens were detected diffusely in the stromal layer. In the lower stromal layer and superficial myometrial layer, type V collagen was detected. Human endometrial epithelial cells performed the re-epithelialization following glandular formation. Rabbit endometrial cells performed also re-epithelialization following the fold formation. The stromal cells were invaded into the inner layer of the folding. Estrogen added to the culture media stimulated the glandular formation. Progesterone administration after estrogen priming did not affect the glandular formation, however, the proliferation of the superficial epithelium and the re-epithelialized area were increased. Rabbit blastocysts successfully attached and implanted into the reconstructed endometrium. The development of the implanted embryos was morphologically normal. Human cultured trophoblast cells attached, invaded and penetrated into the extracellular matrix components. On the other hand, using type V collagen coated dishes, trophoblast cells could invade the stromal layer, however, type V collagen layer did not permit the trophoblast cells to invade into the collagen layer. In vivo, type V collagen, expressed in the lower stromal layer and the surface of the myometrium, may play a role to maintain the early embryo in the decidual compartment. EGTA inhibited the attachment of the blastocysts. Anti-laminin antibody and RGDS peptide, attachment domain of laminin, also inhibited the implantation. These findings suggested that the Ca2+ dependent process was necessary for the attachment between the trophoblasts and the endometrial cells, and then the implantation process was triggered after the attachment to the laminin in basement membrane. The endometrial tissue, obtained from the infertile patient, was cultured on the basement membrane extract with serially obtained maternal serum. Addition of the maternal serum after proper administration of pFSH, high estrogen conditions were made in the culture dishes. These conditions increased the height of the glandular structure and relatively decreased the area of the surface epithelium. Decreased the area of surface epithelium affected the rate of the attachment. Endometrial cell culture system associated with functional and morphological characteristics was established. Serial observation of the endometrial cells in this system revealed the rabbit and the human implantation process, and the embryo-endometrial interaction.(ABSTRACT TRUNCATED AT 400 WORDS)