Culture methods for postimplantation embryos are now widely used in studies of embryo physiology, growth and development. Available methods support growth and development of rat and mouse embryos at all stages of organogenesis. The best results are obtained from embryos between head fold and early limb bud stages; overall growth and differentiation of these embryos in vitro is almost identical to that in vivo. Some examples of the application of postimplantation embryo culture to specific lines of study are given and some possible future developments of the technique are discussed.