Two purposes have guided the writing of this book. Originally, I wanted only to bring together the results which we have obtained during more than ten years of work on evoked potentials in psychiatric disorders. However, it soon became clear that I really wanted to do a little more than that. First of all, a systematic review of the literature seemed indicated. Even though research findings are usually presented in the context of such a review, our laboratory has not studied every aspect of evoked potentials. Consequently, it seemed more appropriate to place our own results within the framework of a general presentation of the evoked-potential field, rather than to have our specific studies govern topic selection. Second, I found that I wanted to expound on the principles and details of techniques to a broader extent than warranted for presenting only our own results. The motivation for attempting such a "methodological primer" came not only from my long-term preoccupation with technical issues, but from contacts with many investigators who consulted me during the early stages of their ventures into evoked-potential research. Thus, to the initial goal of a re- search monograph was added that of a systematic account of both the substantive findings and the methodology of the field.