Placental abnormalities are proving to be a formidable obstacle to overcome in the nuclear transfer process. In the bovine, it is the trophoblast cells which make the major contribution to the parenchyma cells of the placenta. Previous studies have shown trophoblast cells to be feeder layer dependent, and, in the mouse, fibroblast growth factor-4 dependent, to remain undifferentiated and in a proliferating state. To date, t here have been no reports o f a bovine trophoblast cell line that is not feeder layer dependent, nor are there any studies determining the effects of fibroblast growth factor-4 on bovine trophoblast. It would be useful to have a stable line of bovine trophoblast cells, for in vitro studies, to determine if these cells are capable o f contributing the trophectoderm lineage in vitro, and eventually in vivo, t o aid in development of a normal, functioning placenta.