The goal of this book is to provide an integrated overview of some intriguing problems of cardiac electrophysiology. Topics have been selected that encompass mainly aspects which have been a matter of concern and interest in our Department over the past few years. We requested from the authors not only that they provide information about their own investiga tions, but also that they integrate their results with those published by oth ers. Furthermore, we urged them to be speculative in their interpretations in order to encourage exploration of related areas of investigation. To this end, the authors have presented their ,contributions in sufficient detail so that the information may not only educate the reader but also encourage and chal lenge him. It is through the concept of total integration -from in vitro to in vivo, from animal to man, from the pure scientist to the clinician -that we hope to advance our understanding of cardiac electrophysiology. The book brings together scientific work in which important advances have been made in the seventies, and in which even more substantial pro gress is likely to be made in the present decade. The chapters have been written by investigators who are authorities in the relevant scientific field. No attempt at summarizing has been made as this may not seldom lead to oversimplification, a risk that we do not dare take. The table of contents and list of contributors are, in this regard, self-explanatory.