Both sodium restriction and weight loss without alterations in sodium balance have reportedly resulted in blood pressure decrements in hypertensive man. The antihypertensive mechanism of short-term (5-day) sodium restriction was investigated in 38 essential hypertensive adults. The small decrement (6 mm Hg) that occurred in mean arterial pressure during low- as opposed to high-salt intake (35 and 177 mEq/day, respectively) correlated best with plasma volume contraction. Baroreflex sensitivity was unchanged during salt deprivation, while renal hemodynamics actually deteriorated. Inasmuch as rigorous sodium deprivation would result in (1) questionable compliance and (2) a small decrement in arterial pressure at the expense of (3) impaired renal perfusion, the merits of such a strategy as first-line therapy of hypertension should be questioned and confirmatory long-term studies initiated. It should be reiterated that these are short-term findings whose interpretation may not pertain to a period longer than a few days.