Abstract In recent years, it has become evident that the volume of a given cell is an im￾portant factor not only in defining its intracellular osmolality and its shape, but also in
defining other cellular functions, such as transepithelial transport, cell migration, cell
growth, cell death, and the regulation of intracellular metabolism. In addition, besides in￾organic osmolytes, the existence of organic osmolytes in cells has been discovered. Os￾molyte transport systems—channels and carriers alike—have been identified and charac￾terized at a molecular level and also, to a certain extent, the intracellular signals regulating
osmolyte movements across the plasma membrane. The current review reflects these de￾velopments and focuses on the contributions of inorganic and organic osmolytes and their
transport systems in regulatory volume increase (RVI) and regulatory volume decrease
(RVD) in a variety of cells. Furthermore, the current knowledge on signal transduction in
volume regulation is compiled, revealing an astonishing diversity in transport systems, as
well as of regulatory signals. The information available indicates the existence of intricate
spatial and temporal networks that control cell volume and that we are just beginning to
be able to investigate and to understand