This volume represents an interdisciplinary approach to an understanding of the chemistry, physiology, and medical significance of the vitamin riboflavin. Information has been reviewed on the physiological role of the vitamin, the metabolic effects of riboflavin deficiency in animals and man, and the regulation of riboflavin metabolism. In each chapter early background material has been included, but the major emphasis has been on the many recent advances that have been made. The early chapters of the book are concerned with the physical and chemical properties of riboflavin and its coenzyme derivatives and the nature of the interactions between flavoprotein apoenzymes and their coenzymes. The various methods currently available for measuring f1avins in biological tissues, particularly in man, have been described in detail, together with newer procedures that appear to have certain advantages over existing techniques. Chapters dealing with the absorption, excretion, and metabolism of riboflavin provide basic data on the processes involved in vitamin uptake and in metabolic transformations.