The influence of three corticoid-inhibitors (Amphenone, Metopirone and SU 9055) on the corticoid secretion of the domestic pigeon was studied on a comparative basis. The level of corticosterone was reduced considerably with Amphenone and Metopirone; SU 9055 induced a rise. The ‘cortisol (?) level was reduced moderately with the three inhibitors. The findings on corticosterone only were statistically significant. The implications of these results have been briefly discussed. © 1967, The Japan Endocrine Society. All rights reserved.