The goal of the review is to describe methods available for use by research workers interested in studying the site and/or mode of action of compounds that might perturb the function of membranes in the nervous system. Many, or even most, neurotoxic agents may eventually bring about some perturbation of membrane structure, composition, or function. It is difficult to differentiate those changes mediating, from those compensating for, toxic insults. The review is limited to a discussion of certain approaches and methodologies believed to be important for studying these problems. Some examples of how these biochemical approaches may be used to define membrane-related abnormalities subsequent to exposure to a toxin are also given. Emphasis is placed on those methodologies and results that may be related to neurotransmission.