The effect of captopril on the response of plasma aldosterone (PA) and plasma renin activity (PRA) to 10 mg metoclopramide i.v. was studied in 9 normal subjects. In the same conditions the prolactine response was studied in 6 healthy males. Metoclopramide induced a significant increase of PA during control study, as well as after treatment with captopril. The maximal increase of PA was of similar magnitude and occurred 15 mn after injection of metoclopramide on both occasions. PRA did not change appreciably after metoclopramide neither during control study nor during captopril. The prolactin response to metoclopramide was blunted by treatment with captopril. In conclusion, captopril did not alter the aldosterone response to metoclopramide, which suggests that dopaminergic control of aldosterone secretion is independent of modifications in the renin-angiotensin system.