Twelve years have elapsed since the appearance of the first volume and it is with great pleasure that the Editor is now able to present volume 15. During these twelve years various fields of drug research have undergone important, partly revolutionary, changes. A number of these have already been dealt with, so that the series PROGRESS IN DRUG RESEARCH contains a comprehensive review of a substantial part of our current knowledge. The Editor is particularly grateful for the opportunity of transmitting to those connected with the development of drugs the extensive knowledge of the Authors, who, without exception, are themselves actively engaged in research. Drug research is currently in a state of transformation: reconsideration in the light of the past and reorientation with a view to the future. To a large extent this is due to the tumultuous developments in the last 20 years, developments which are unparalleled in the history of medicine and the consequences of which cannot yet be completely evaluated. Unfortunately, however, the current situation is not devoid of its unpleasant and even tragic aspects, aspects which fall outside the research worker's sphere or influence. Those connected with drug research, be they in industry, in universities or in clinics, are aware of these problems, and, as a result of this awareness, are all the more in need of an aid which will assist them in ascertaining the current position and in fixing future goals.