A culture method for mouse embryos of post-implantation stage has not yet been established. In this study, we tried several methods of mouse embryo culture from blastocyst to early-somite stage using co-culture technique, human cord and/or rat sera and cytokines including leukemia inhibitory factor (LIF). Among feeder cells examined, placental cells appeared to secrete some factor (s) to promote post-implantation development. Among the sera examined, human cord serum supported best the post-implantation development. Although LIF seemed to promote pre-implantation development and implantation, it did not support post-implantation development. The present culture system is thus useful for observing embryos for two to four days after implantation. Using this system, Lim-1, a LIM class homeodomain-containing transcription factor, was observed in a part of the embryo and is suggested to play a role in early embryogenensis.