1. β-Lipotropin has a potent aldosterone stimulating effect in vitro and in vivo in rats.
2. The maximum aldosterone response to β-lipotropin was the same as to ACTH and greater than to angiotensin II.
3. Although doses of ACTH which maximally stimulated aldosterone significantly increased cyclic AMP production, maximally stimulating doses of sheep β-lipotropin did not increase cyclic AMP production significantly.
4. These data suggest that β-lipotropin may play a role in aldosterone regulation through a mechanism different from that of ACTH.