It is generally appreciated that large congresses are not the optimal means of facilitating communication within specialized areas of medical research. Small symposia, where scientific discussion can be confined to limited groups, have lately become successful vehicles of information transfer. However, such symposia, although eminently suited to the exploration of specific problems, often have the llherent'disadvantage of not being able to successfully address themselves to larger themes. Accordingly, the planners of this symposium have solicited the parti- cipation of internationally acclaimed investigators to consider current problems both in the physiological and clinical domains of nephrology. The observant reader will note that the variety of theoretical and experi- mental approaches used by the physiologists are reflected in the clinical studies, while the clinicians, in turn, have provided the physiologists with useful insights. The part of the symposium which attempted to correlate metabolic characteristics of kidney cells with their transport functions has proven to be particularly fruitful. For example, the presentations dealing with aldosterone, angiotensin and diuretics have offered a multi-faceted approach that was previously unavailable. The contributions of investigators from many countries and their enthusiastic participation have led to the success of this symposium. To them we wish to express our deep gratitude. We also wish to sincerely thank Dr. K. H. BEYER, Senior Vice President of Merck, Sharp & Dohme Research Laboratories, and Dr. H. F. HOFMANN, Director of Medical Research of Sharp & Dohme GmbH for their full support and their constant attention to our many requests.

Recent experimental and clinical research performed by outstanding authorities has enabled us to characterize fundamental processes that govern the regulation of salt and water content of the body. Their results have provided not only an important gain of insight into mechanisms at the cellular level but also the possibility to integrate single cell activities into a complex organ function. Moreover, this knowledge enables scientists to develop broader concepts concerning the regulation of organ function and thus contributes to a better understanding of the overall status in health and disease. In the present volume some of these physiologists and clinicians discuss principal questions of humoral and non-humoral influences involved in the control of electro lyte and fluid content of the organism. It contains three essential topics: Data concerning basic principles of cell behaviour and transport processes are followed by the description of natriuretic substances and their influence on volume regulation. Finally, attempts are undertaken to elucidate the meaning of these basic principles for the explanation of the development of patholocigal states. This symposion was held in honor to Professor H. P. Wolff, one of the internatio nally wellknown pioneers in this field of clinical research. The editors. wish to express their graditude to the Melusin-Schwarz-Monheim GmbH for the generous support of the symposion."