In this study we have investigated the effect of co-dergocrine, a selective DA2-agonist, on plasma aldosterone concentrations (PAC) in twelve patients with essential hypertension both in basal conditions and during sodium depletion. Sodium depletion resulted in an increase of PAC from 38 (13) pg/ml to 297 (21) pg/ml. The PAC response to sodium depletion was reduced to 155 (29) pg/ml by co-dergocrine. No significant PAC changes were found in patients maintained on a normal sodium intake. In addition the drug did not significantly modify plasma renin activity (PRA) in either experimental group. These results suggest that the dopaminergic inhibition of aldosterone secretion in man is mediated by DA2 receptors in the adrenal cortex.