A great deal of evidence has been presented which suggests that a generalized increase in cell membrane permeability to various ions is a fundamental defect associated with hypertension. In addition, some of the evidence is supportive of a central role of this defect in the pathogenesis of hypertension. The source of this defect may lie in the reduced calcium binding capacity of the cell membrane. Because of this reduced capacity the membrane is less stable and is more permeable to various ions.