In healthy women during moderate hydrosaline retention we have evaluated the antagonistic effects of sulpiride – enantiomers and racemic – on the renal action of a low-dose dopamine (DA) infusion (0.1 μg/kg/min). The studies were performed, in hypotonic polyuria, by the clearance (Cl) method in (1) hydrosaline retention (n = 23), (2) retention + dl-sulpiride (n = 8), (3) retention +d-sulpiride and (4) retention +l-sulpiride (in the latter two cases n = 7 subjects submitted to paired studies). Hydrosaline retention was induced by deoxycorticosterone acetate treatment. A common pattern of sulpiride treatment was applied. The DA renal hyperemia is abolished by l-sulpiride while it is transitorily attenuated by d-sulpiride. In both conditions 3 and 4 the increase in glomerular filtration rate, the inhibition of fractional isosmotic sodium reabsorption and the increase in urinary sodium excretion – induced by DA in condition 1 – are suppressed. On the contrary, DA inhibition of fractional anisosmotic sodium reabsorption is not affected by sulpiride. The data indicate that DA renal hyperemia results from the action of DA on DA2 receptors; the DA inhibition of sodium transport by the diluting segments does not appear to be mediated by typical DA r