A tissue culture system of the rat embryonic central nervous system is described which allows morphological, biochemical, and electrophysiological approaches. Examples for each of the mentioned methods are given. Developmental features of these cultures are described as they appear in the phase contrast microscope over a period of 4 weeks. Further details are shown by a scanning electron microscopic photograph. Tetanus toxin induced changes in acetylcholine synthesis and release serve to demonstrate the usefulness of the model system for biochemical approaches. Intracellular recordings of neurons reveal synaptic potentials as well as spontaneously fired action potentials. Thus an ample use of rat central nervous system cultures in pharmacology and toxicology should provide completely new insights into the action of drugs and toxins at the cellular and molecular level.