INTRODUCTION MANY workers have observed the adrenal lesion accompanying pantothenic acid deficiency in rats (Daft and Sebrell, 1939; Nelson, 1939; Ashburn, 1940; Deane and McKibbin, 1946). Briefly the lesion consists of congestion of the inner cortical zones with hemorrhage, necrosis, fibrosis, hemosiderin deposition and calcification. The medulla and zona glomerulosa are rarely involved. However, the mechanisms involved in the development of this lesion have received little attention. Adrenal cortical extract, desoxycorticosterone and anterior pituitary extract failed to modify the adrenal lesion in pantothenic acid deficient weanling rats (Mushett and Unna, 1941). Unpublished experiments of a similar type in our own laboratory were likewise unsuccessful. In the course of these experiments it occurred to us that two things might be needed—first, larger doses of more highly purified hormone preparations and, second, a more uniformly severe deficiency state in our rats. The latter became available with the technique described by Nelson, et al. (1950). After these two factors had been taken into account and proper formulation of the experiments here reported, we were able to modify in significant degree the adrenal lesion.