It is a pleasure to have the privilege of writing the foreword for a book edited by Dr. Francis F. Foldes. Dr. Foldes has collected in one convenient place a discussion and description of enzyme systems of use to the anesthesiologist and to those other individuals, such as undergraduate and graduate students in related basic sciences, who will profit by and can make use of this body of information. The practicing anesthesiologist and those who work in related fields have become increasingly aware of the need to understand enzyme activities which influence the uptake, distribution, and excretion of those substances that are used in the anesthetic management of surgical patients. A variety of such is obvious when one considers that such diverse substances as activities and muscle re analgesic drugs, tranquilizers, hypnotics, anesthetic agents, laxants are strongly affected by these systems and have an influence over the basic understanding of how these drugs operate and act in the body, as well as providing a safety measure so necessary to the proper conduct of clinical anesthesia. The editor and his colleagues have rendered us a great service in collecting information that deals with the basic activity of enzymes including their structure, their kinetics, and to the degree that knowledge permits, mechanism of actions.