By the method of single preimplantation embryos differential display polymerase chain reaction (SPEDDRT-PCR), 25 reprogramming cDNA fragments were obtained from single 2-cell, 8-cell embryos and blastula. After cloning and sequencing, five of them were identified by reverse-Northern and characterized with stage-specific expression during reconstructed embryo development. This results will help to isolate full length reprogramming genes and study their function during embryonic development.