Cell Membranes: Methods and Reviews is the continuation of a distinguished series of books edited by Edward Kom under the title Methods in Membrane Biology. While the original series nominally dealt with methods for the study of membranes, its chapters were, in fact, much broader and covered the conceptual framework upon which the methods were based as well as the methodology per se. In continuing this series, we changed the title to reflect this broader point of view. We hope to present a series of volumes published at roughly annual intervals containing comprehensive reviews dealing with various aspects of membrane biochemistry. We will on occasion also include short chapters that deal exclusively with new methods and their applications. The biology of membranes as we view it is very broad and we hope therefore not only to include work that is directly related to molecules present in membranes but also to treat molecules that interact with membrane compo­ nents. In each of the volumes we hope to have one or two areas of concen­ tration and to include chapters that collectively present a balanced and com­ prehensive review of those particular fields. In this first volume, we have concentrated on transport of solutes across the membrane. We are grateful to the authors, who have provided us with excellent and comprehensive chapters in these areas in a timely fashion.