Eight normal women took part in a randomized crossover study to investigate the effect of dietary supplementation with 105 mEq sodium chloride (NaCl) for 3 days or equimolar sodium citrate (NaCit) after salt depletion. NaCit supplement induced greater urinary sodium and potassium excretions than did the NaCl supplement (197 +/- 10 v 107 +/- 19 mEq/3 days for sodium, P less than .01, 130 +/- 7 v 96 +/- 6 mEq/3 days for potassium, P less than .01, respectively) and less body weight gain (+0.6 +/- 0.1 v +1.6 +/- 0.1 kg, P less than .01). Suppressions of plasma norepinephrine, renin activity and aldosterone concentration were significantly smaller with NaCit than with NaCl supplement. We conclude that the anionic component of sodium salts may have some effects on renal sodium handling and modulates volume expansion and humoral factors.