SUMMARY: Angiotensin II administered intravenously in doses of 40–50 μg./100g. body weight produced a significant increase in the capacity of the adrenal glands of rats to synthesize aldosterone. An increase in the production of corticosterone was not significant. The changes occurred about 24 hr. after the last injection of angiotensin, when the circulatory effects of the drug had ceased. Since adrenocorticotrophic hormone (ACTH) with aldosteronotrophic activity, administered intravenously, did not result in increased steroid synthesis by the adrenals, it is unlikely that the phenomenon is due to mobilization of endogenous ACTH. Angiotensin added to adrenal slices in vitro failed to produce the stimulating effect seen in vivo. Further investigations are needed to explain this difference.