A discussion of the applicability of in vitro techniques now available for research in prenatal toxicology is presented. Advantages and disadvantages of the various in vitro methods (such as cultivation of preimplantation embryos, whole embryo culture, and organ culture) as applied to various problems of experimental research are described. As a typical example, the experience gained in our laboratory with the organ culture of mammalian limb buds is detailed. Various aspects of the research with this type of organ culture - e.g., different techniques of culturing, extent of differentiation achieved in culture, induction of abnormalities in culture, supplementing the system with drug-metabolizing capacities and means for quantification of the data - are discussed. It is concluded that certain in vitro techniques using mammalian embryonic tissues are very suitable tools for elucidating the mode of action of teratogenic agents, and that they may serve as a "model" for several basic processes also for the situation probably existing in humans. Such organ culture, and other in vitro methods, provide little, if any advantage over in vivo experiments if a "mass screening" of a possible teratogenic potential of chemicals (hazards for the human population) is attempted.