Rigorous sodium deprivation can lower the blood pressure of some patients with essential hypertension (at best, 30% to 50% of patients). In the rest, sodium depletion is ineffective and, in some instances, can raise the blood pressure and cause adverse clinical effects. In normal persons, it is difficult to affect blood pressure even with drastic changes in salt intake; for the blood pressure to rise even slightly, it may be necessary to consume more than 800 meq/d. There is no evidence to indicate that a widely applied, moderate reduction of salt intake could prevent the development of hypertension. The evidence suggesting that such moderate salt intake would significantly lower blood pressure in the patients with sodium-sensitive essential hypertension is weak. Human hypertension comprises a heterogeneous spectrum of abnormal vasoconstriction-volume interactions. Sodium deprivation, like other forms of therapy, should be applied only to those patients in whom its effectiveness has been established.