Gene Targeting and Embryonic Stem Cells is a practical guide designed for the rapidly growing number of researchers who are moving into this field. Details are provided on how to culture, transfect and differentiate established cell lines, and how to isolate new cell lines. Gene targeting experiments are described for a number of cell types, including ungulate fetal fibroblasts, murine ES cells, human embryonal carinoma cells and human ES cells, and include protocols for gene-targeting vectors, DNA transfection and RNA interference.