The response of blood eosinophiles to ACTH and epinephrine was studied in 3 patients with adrenocortical insufficiency, 9 cases with either pigmentation or hypotension suggesting adrenal cortical insufficiency, and 9 miscellaneous patients. Following ACTH (20 mg. subcut.) the maximal fall in the circulating eosinophiles was 18%; in only 3 patients not believed to have adrenocortical disease was the eosinophile reduction less than 50% (41%-myxedema; 44%-diagnosis unknown; 37%-asthma). Epinephrine (0.3 mg. subcut.) caused a reduction of more than 50% in 1 patient with proven adrenal tuberculosis. The maximum effect was seen from 2-6 hrs. after admn. of the test hormone. Significance of the test would be increased by frequent eosinophile counts.