Based on previous studies, mRNA differential display using a single mouse oocyte or a 2-cell embryo as starting materials was established. cDNA fragments, which were expressed in 2-cell stage mouse embryos but not in MⅡ stage, were performed computer cloning and GenBank search. Two genes, NADH dehydrogenase gene subunit-2 and ATPase-6,which encoded by mitochondrial genome, were found to be stage-specifical expressed in 2-cell-stage pre-implantation embryos. These results, which were the same as multi-embryonic mRNA differential display, strongly suggest that single preimplantation embryos differential display polymerase chain reaction (SPEDDRT-PCR) is a credible, practical and effective method that needs only a single embryo.