SUMMARY Plasma catecholamine and renln activity levels were measured across a range of dietary sodium intakes (10-300 mEq/day) In 20 normal male volunteers. Supine plasma norepinephrine levels presented a triphasic pattern in relation to urine sodium, whereas epinephrine levels were Dot significantly altered by sodium intake, and renin showed the well-known hyperbolic relationship to urine sodium excretion. Highest supine norepinephrine values occurred at low salt intakes, the lowest when sodium excretion was between 100 and 180 mEq/day, and intermediate when sodium excretion was greater than 180 mEq/day. These findings show that sodium intake is an important consideration in the interpretation of plasma norepinephrine levels.