This book deals with the life and work of Nathan Zuntz and specifically addresses the contribution he made to high altitude physiology and aviation medicine. While some of the material on this topic has already been published in English (Gunga and Kirsch, 1995a, 1995b), the overwhelming majority of it is only available in German (Gunga, 1989). Recently, new and interesting sources on the life and work of the Berlin physiologist have come to light. That was why the author gladly accepted the invitation from the History Book Committee of the American Physiological Society in 2005 to write a biography of Nathan Zuntz. The result is a completely new, revised version of the book which is based on more than twenty years of study on the life and work of this physiologist. This biography could not have been written without the help of numerous people and institutions. First, I would like to thank Dr. John West, the current Chairman of the APS History Book Committee, who personally committed himself so firmly to making this project possible from the very first day. I am very grateful to the Free University, the Charite, the DLR (German Aerospace Center) in Cologne and the management in Bonn-Oberkassel ­ namely Dr. Horst Binnenbruck, Dr. Peter Preu, Prof. Dr. Günter Ruyters, Dr.