Efforts to measure neurotransmitters and related s- cies in living brain tissue by faradic electrochemistry began in earnest in the early 1970s. During the ensuing years, s- eral monographs and various symposia on the subject have appeared. The present volume of Neuromethods, Voltammetric Methods in Brain Systems, can be considered different from previous offerings in several respects. The methodology of in vivo electrochemistry has now reached a stable level of maturity. It is no longer necessary to convince interested re- ers that the techniques can measure, with specified degrees of reliability, certain neurotransmitters and metabolites in the extracellular fluid space. Moreover, the basic approaches of electroanalytical measurements are more widely appre- ated by neuroscientists and one need not explain in tutorial fashion the details of oxidative electrochemistry. Nevert- less, in keeping with the nature of the Neurumethods series, this is a "how to" volume and readers will find ample detail on the preparation of electrodes, practical experimental details, and the interpretation of results. But the emphasis is strongly on the application of voltammetric methods. The first two chapters deal with fundamentals inherent in employing in vivo electrochemical measures. The first - ticle offers an authoritative account of our understanding of the surface states of carbon and carbon fiber electrodes. It provides a rationale for the various pretreatments that have allowed the "tuning" of electrode properties to obtain sen- tivity and fast response times.