This book arose from a meeting held at the University of Washington, Seattle, in July of 1986. The meeting was a satellite symposium of the XXXth International Congress of Physiological Sciences which occurred in Vancouver, canada, at that time. 2 Adjustments in the cytoplasmic Ca + concentration of cells occur in response to a variety of external signals. These fluctuations are a cen­ tral component of one mechanism by which cells adapt their activities to changes in the external environment and to the requirements of whole body 2 homeostatic mechanisms. It is now clear that redistribution of Ca + within 2 intracellular compartments, as well as changes in the rates of Ca + influx and extrusion at the whole cell level, occur during signal-dependent 2 changes in the cytoplasmic Ca + concentration. In summarizing current research in this area, this volume considers first the properties of individual cation transporting activities located in various cell membranes. It then moves to the cellular level, where the consequence of individual transporting activities acting in concert is examined. l!D.phasis is also 2 p1 aced on pa tho1 ogica1 conditions which resu1 t in loss of cell Ca + regu1 a­ tion as a part of the disease process. We hope that this approach will help the reader to integrate developments in this large and rapdi1y changing fie1 d.