Biological cell membranes regulate the transfer of matter and informa- tion between the intracellular and extracellular compartments as basic survival and maintenance functions for an organism: This volume contains a series of reviews that are concerned with how biological plasma membranes regulate the transport of chloride between the intracellular and extracellular compartments of a cell. This book is also an attempt to analyze the molecular basis for the movement of chloride across a cell membrane. This volume is devoted to a diversity of electrogenic chloride transport mechanisms in representative cell membranes of all living things. The first section of the book (Chaps. 1-4) focuses on mech- anisms of primary active chloride transport (i.e. photon or A TP-driven), while the second section (Chaps. 5-6) centers on secondary active chloride transporters (symport and antiport) in both plant and animal plasma membranes. The last section, which comprises seven chapters (Chaps. 7-13), deals with chloride channels in cell membranes of prokaryocytes and eukaryocytes of most every phylum. It is hoped that with this particular ordering the reader can glean a telescopic view of the evolutionary history of the various electrogenic chloride transporters.