This little book was assembled from the authors' lectures to medical students and was originally published as one volume in the series Human Physiology, edited by O. H. Gauer, K. Kramer, and R. Jung. The editors intended that each volume in this series be independent of the others and we have kept to this purpose. We have included here only material that we feel is necessary for medical students to know in order to understand kidney function in health and, by later extrapolation, in disease. The contents rest on accepted principles estab- lished by experiments, and little space is given to what is controversial, hypo- thetical, or unresolved. We are pleased that Dr. Coxon has been motivated to prepare an English language version of this text. We hope that it will serve as a ready reference and review source for the beleaguered medical student. P. Deetjen J. W. Boylan K.