This chapter describes the application of electrophysiological techniques in nervous system cultures. The characterization of the membrane properties of cultured neural cells with electrophysiological techniques had already started in 1956 on explant cultures of dorsal root ganglion cells (Crain, 1956) and on glial cells from the cerebellum and midbrain of the kitten (Hild et al., 1958). Subsequently, membrane properties of neurons and glial cells from different areas of the brain were characterized with a combination of electrophyslological, morphological, and immunocytochemical methods.