For decades excess sodium intake has been implicated in the etiopathogenesis of high blood pressure. Data from epidemiological, clinical, and animal experimental studies all suggest a direct casual association between excess salt intake and hypertension. Several investigators suggest that hypertension is the result of an inability of the kidney to excrete salt and water normally. It is hypothesized that the development of chronic blood pressure elevation results from the kidney's need to increase urine volume and sodium excretion -- in the presence of habitual high sodium intake -- in order to maintain homeostasis of the extracellular fluid volume.