The behaviour of plasma renin, aldosterone, cortisol and prolactin after administration of a drug with antidopaminergic action, metoclopramide, was evaluated in 6 normal subjects, 8 patients affected by primary aldosteronism and in 5 patients affected by anterior hypopituitarism. In the first two groups, besides the predictable increase of prolactin under metoclopramide, a significant aldosterone increase was noted. Cortisol remained unchanged, and PRA was not significantly increased. A similar pattern of aldosterone, cortisol and PRA was also found in patients with hypopituitarism. However, the plasma prolactin did not increase in this group. The comparative examination of three groups of patients leads us to conclude that aldosterone increase is not imputable to ACTH, renin or to prolactin. This may be explained by a possible direct effect of the antidopaminergic drug at the adrenal level, which is more likely than an effect through some yet undetermined factor.