The maintenance of a stable acid-base status within biological tissue is a fundamental homeostatic process in all organisms, necessary to preserve the metabolic function of proteins and other macromolecules. The study of acid-base regulation has advanced enormously over recent decades due to the development of increasingly accurate and sensitive techniques for measuring acid-base variables. This volume brings together contributions from leading comparative physiologists working on factors affecting the acid-base status of the internal fluids of animals and plants. The result is a broad-ranging, authoritative and accessible review of this area, together with a critical look at techniques and tools.