The water proton spin-lattice relaxation time (T(1)) in mammalian cells and tissues has been measured as a function of external ion concentration and total cell water content. The results can be interpreted in terms of changes in the fractions of bound and unbound water, and changes in the coordination shells of macromolecules due to alterations in macromolecular configuration caused by changes in salt molarity and the amount of water. It is shown that the direct effect of the ions (Na(+), K(+), Li(+), Cl(-)) on structuring cellular water, i.e., into ion coordination shells, is small; the main effect of these ions on cellular water structure is an indirect one, resulting from their capability of changing macromolecular coordination shells.