As technology has become more refined and available in recent years, a major focus for neurotoxicologists has been the evaluation of toxicant effects on neuronal function. This interest will probably increase as the number of new chemical messengers (i.e., neurotransmitters and neuromodulators), and our understanding of their function, expands. Other chapters in the volume provide data related to many specific neurotoxicants, and while also discussing specific issues, this chapter will emphasize some important philosophical points which are underscored by these studies. The presentation will attempt to highlight those strategies that have yielded valuable insights into mechanisms of toxicity, as well as approaches that have been, in the authors' judgment, less productive. (Copyright (c) Raven Press, New York 1984.)