In this study, we sought to determine the extent to which mitogenic growth factors affect the survival and development of cloned mouse embryos in vitro. Cloned embryos derived by intracytoplasmic nuclear injection (ICNI) of cumulus cell nuclei into enucleated oocytes were incubated in culture media supplemented with EGF and/or TGF-alpha for 4 days. Compared to control, treatment with either growth factor significantly increased the blastocyst formation rate, the total number of cells per blastocyst, the cell ratio of the inner cell mass and the trophectoderm (ICM:TE ratio), and EGF-R protein expression in cloned embryos. In most instances these effects were enhanced in cloned embryos when EGF and TGF-alpha were combined. Although fewer blastocysts developed from cloned than from fertilized one-cell stage embryos, growth factor treatment appeared to have the greatest effect on cloned embryos. These results demonstrate that mitogenic growth factors significantly enhance survival and promote the preimplantation development of cloned mouse embryos.