Volume XXV of the Handbook of Experimental Pharmacology series entitled "Bradykinin, Kallidin, and Kallikrein" was published in 1970. My aim in editing this volume of the series is not to replace, but to update the 1970 edition. During the decade preceding the publication of Vol. XXV, the existence of kinins and kallikreins gained acceptance, the protein components of the system were purified and characterized and the peptides were synthesized. Even after these accomplish ments, interest in the subject has not abated, but has increased substantially. We have learned a great deal about the role that components of the kallikrein-kinin system play in other systems and about the immensely complex and intricate inter actions in blood. Directly or indirectly, kallikrein and kinins affect the coagulation of blood, the activation of complement, and the generation of angiotensin. Kinins release or modulate the actions of other agents, including prostaglandins, histamine, and catecholamines. Inhibitors of kallikrein or kininase II are employed, for example, in extracorporeal circulation or in hypertension. Kallikrein, kinins, and kininases, present in urine, were described first in 1925 and 1954, but have been ignored for decades. These substances are now studied extensively because of their possible role in blood pressure regulation. The evidence that kinins have a metabolic function is also increasing. The abundance of active components of the system in genital organs suggests a role in the fertilization process. The book is organized into chapters which bear upon these issues.

The papers collected in this volume were presented at the International Symposium on Hypotensive Peptides held in Flor ence, Italy, on October 25-29, 1965. The purpose of the meeting was to bring together scientists of fourteen countries ranging from the chemist to the surgeon, who usually do not speak a common language and for whom it would be quite difficult to follow the latest developments in fields allied to, but still some what removed from their basic interest. Their reports sum marized their recent progress and current achievements, and gave indication of the trend that future research on hypotensive peptides may take. Various aspects of the structure and function of brady kinin, kallidin, kallikrein, gastrin, eledoiSin, physalaemin, sub stance P, and related substances were discussed during the nine sessions. The first session was devoted to the chemistry of peptides. This was followed in loose order by reports dealing with the structure of some newer peptides, with kininogen, and with enzymes that release or inactivate peptides. Subsequently, reports on the physiological, pharmacological, pathological, and clinical importance of kinins, kallikrein, and eledoisin were presented. One entire session was devoted to substance P. At the closing session two motion pictures demonstrated the effect of the peptides on the circulation. The appendix of this volume contains the report of the international Committee on Nomenclature."