Cells from the nervous system can be grown in culture and exhibit many of the biophysical, biochemical, and morphological properties found in vivo. They can be induced to differentiate in culture and perform some of the interactions that occur in the nervous system, including synaptogenesis. A number of important questions relating to nervous system development and function have been approached in culture in ways that cannot be done in vivo. The use of clonal cell lines should lead to rapid progress in the analysis of the nervous system at the chemical level.