The basic principles of the phenomenon "erection" have been known since the pioneering work of Kolliker, Eckhard and Langley in the nineteenth century. Nonetheless, under the influence of Freud, erectile dysfunction was predominantly at­ tributed to psychogenic factors. A more liberal perception of sexuality since the 1960s, the development of new and refined diagnostic techniques, and the expansion of basic research activity resulted in a new concept of erectile dysfunction, identifying arteriogenic, venogenic, endocrinologic or myopathic (cavernous smooth muscle dysfunction) factors. From this research other considerations such as autonomic innervation, cavernous endo­ thelial intactness or impaired neurotransmitter pool are being introduced into routine clinical assessment. A reevaluation of psychogenic etiology with a consequential new concept of psy­ chogenic impotence is on the rise. In this book the new concepts of basic knowledge on cavernous smooth muscle function and its supraspinal, spinal, and local control; the new diagnostic approaches in psychogenic and autonomic factors; and the new developments of reconstructive therapeutic options for the patient have been tied together. Outstanding and internationally renowned experts in the field of erectile dysfunction have given detailed insight into the latest basic and clinical developments. Well-established diagnostic and thera­ peutic techniques are presented by experienced colleagues. We hope that this book will help the reader to get an overview of the current concepts of erection. Furthermore, we hope that international collaboration in basic and clinical research in the field of erectile dysfunction will render an update necessary in the near future.