We tested the effect of dietary potassium (KCl, 20 mEq three times daily), calcium (Ca, 500 mg twice daily), sodium-potassium-dependent ATPase inhibition (digoxin), calcium channel blockade (nifedipine), and placebo on acute natriuresis in 14 normal subjects who received 2 L normal saline intravenously over 4 h. Plasma renin activity (PRA) was increased in subjects receiving nifedipine, while plasma aldosterone (PA) concentrations were not different among the regimens. Only KCl and nifedipine affected sodium excretion compared to controls. KCl and nifedipine increased the amount of sodium excreted after the infusion was terminated. In the case of nifedipine, this natriuresis was sufficient to increase the 24 h sodium excretion on that day to above that of the other regimens.