An improved method of cloning mammalian embryos by transferring a nucleus from a donor mammalian embryo to an enucleated recipient oocyte and culturing the nuclear transferred bovine embryo in vitro is described. The improvement includes positioning the donor embryo nucleus adjacent to the enucleated recipient oocyte, and maintaining the nucleus and oocyte in a maintenance medium for a time sufficient to mature the cytoplasm of the enucleated recipient oocyte prior to fusing the donor nucleus to the recipient oocyte.
