This book first appeared in English in 1983, as a translation of the 20th Edition of the long-established German textbook Physi%gie des Menschen. In this new English edition the text has been fundamentally "rejuvenated", to bring it up to date with the rapid advances in many areas of physiology and to incorporate many helpful suggestions from both readers and colleagues. In its scope and didac tic goals, the book remains as we set forth in the Preface to the First Edition, which follows. First, the content was substantially reorganized. The general aspects of cell physiol ogy and intercellular communication, which underlie the functions of all organs, were extracted from the various chapters and brought together in a separate intro ductory section. We are most grateful to our colleague J. DUDEL for undertaking this task. The second step was to make the text more concise in several places (for instance, the motor and somatovisceral systems previously occupied two chapters and have now been condensed into one). By these processes of condensation and distillation of the passages on general cell physiology, space was made for the necessary addi tions and expansions, with only a slight change in the overall length of the book.