The study of the actions of drugs on smooth muscle has been a preoccupation of many pharmacologists almost from the beginning of the discipline. To a con­ siderable degree, the development of theories to explain drug actions on smooth muscle has occurred somewhat independently of the development of our knowledge of the physiology, biochemistry, and biophysics of smooth muscle. This knowledge has developed rapidly in the past decade, and some of its consequences for our understanding of drug-receptor interactions in smooth muscle have not always been fully appreciated or accepted. One of the purposes of this volume is to provide pharmacologists with some understanding of the physiology, biophysics, and bio­ chemistry of smooth muscle and of related advances in methodology so as to facilitate the incorporation of such knowledge and related methods into future pharmacological studies of smooth muscle and drug interactions. Another purpose of the book is to provide both graduate students and in­ vestigators in pharmacology and related disciplines with a summary of the numerous methods that have evolved or are available for the study of drug and smooth muscle interactions, and, in particular, to highlight their possible uses and limitations. Perhaps, because of the diversity in content and difficulty of these methods, there has to our knowledge never been a previous attempt to bring them together in one place. We have not, of course, succeeded entirely in this objective.