The romantic phase of membrane biochemistry characterized by conceptual develop- ments and an essentially unlimited freedom of choice is gradually coming to a close. Attention is turning from the general, qualitative description of membrane structure toward the specific properties of membrane-linked enzymes and metabolic systems. The purpose of this series is to serve this development by collecting and evaluating the mass of interesting information that is already available widely scattered in the literature. The emphasis will be upon a comprehensive treatment of membrane- linked enzymes from the viewpoint of modern enzymology. The general properties of membranes will be mentioned only to the extent that they are relevant to the dis- cussion of the enzymes in question. The first of the four volumes will deal with the physical and chemical techniques (X-ray crystallography, nuclear magnetic and electron spin resonance, fluorescence spectroscopy, immunology, etc.) used in the characterization of membrane enzymes. Chapters are also included on artificial bilayer membranes, chemical modification of membrane enzymes, and on the nature of lipid-protein interaction in membranes. In the next three volumes the enzyme systems participating in the biosynthesis of cell components, active transport, oxydative phosphorylation, and photosynthesis will be analyzed. A brief discussion of hormone receptors is also included. Subsequent volumes may fill in the few but significant gaps in the coverage that for various reasons could not be avoided.