The long-term stationary culture of postimplanatation embryos without extraembryonic membranes is a method to assess their developmental potential in vitro. The method was almost exclusively used on rat embryos, while mouse embryos were considered unsuitable due to their poor differentiation. In present study the postimplantation mouse embryos were used to verify potential of this method in mice. In addition, the course of in vitro differentiation was compared to embryo development in situ. Embryos were cultivated for maximum of 14 days and morphology and differentiation was analysed on serial semithin sections. Although anatomical relationships were lost from the beginning of the cultivation, the differentiation was only delayed, and the developmental potential after long-term culture was comparable to those observed in rats. Therefore the advantages of long-term cultivation could be utilized to analyse the differentiation of numerous lines of genetically modified mice with impaired postimplantation development.