The in vitro effects of 13 indole compounds on the synthesis of glucocorticoids and of adrenal androgens in sheep adrenal glands has been studied from 11 ‐deoxycortisol as a precursor. This work demonstrates the activating effect of some indole compounds on 11β‐hydroxylase and 17,20‐desmolase and the inhibitory effect of most of them on 11β‐hydroxysteroid dehydrogenase. Three categories could be distinguished: 1) compounds without any effect (5‐hydroxytryptophan, 5‐hydroxytryptamine); 2) compounds moderately increasing (10—30% as compared with controls) Cortisol yields (tryptamine, melatonin, 6‐hydroxymelatonin, 5‐methoxytryptophol, indomethacin); and 3) compounds markedly increasing (80–100%) Cortisol yields (5‐methoxyindole acetic acid, 5‐hydroxyindole acetic acid, 2‐methylindole, 5‐hydroxytryptophol, N‐acetyl‐5‐hydroxytryptamine). In fact, since most of the studied indoles reduced 11β‐hydroxysteroid dehydrogenase activity, the actual activation of Cortisol synthesis was four to five times less. Lastly, all the studied compounds, but melatonin, increased the activity of 17,20 desmolase as seen from 11β‐hydroxyandrostenedione and 11‐ketoandrostenedione yields. The possible in vivo effects of the indoles for therapeutic use needs further studying.