The growth of neurochemistry, molecular biology, and biochemical genetics has led to a burgeoning of new information relevant to the pathogenesis of brain dysfunction. This explosion of exciting new information is crying out for collation and meaningful synthesis. In its totality, it defies systematic summa tion, and, of course, no one author can cope. Thus invitations for contributions were given to various experts in areas which are under active investigation, of current neurological interest, and pregnant. Although this project is relatively comprehensive, by dint of size, other topics might have been included; the selection was solely my responsibility. I believe systematic summation a virtual impossibility-indeed, hardly worth the effort. The attempt to assemble all of the sections involved in a large treatise with mUltiple authors inevitably results in untoward delays due to the difference in the rate at which various authors work. Therefore, the following strategy has been adopted: multiple small volumes and a relatively flexible format, with publication in order of receipt and as soon as enough chapters are assembled to make publication practical and economical. In this way, the time lag between the ideas and their emergence in print is the shortest.