The suggestion that the pathogenesis of adrenal-regeneration hypertension might involve sensitization to the hypertensive properties of corticosterone by the period of cortical insufficiency which follows adrenal enucleation has been investigated. Nonhypertensive doses of corticosterone were given to uninephrectomized, salt-treated and adrenalectomized rats after periods of insufficiency of variable length and to similar rats bearing regenerating adrenals, beginning such treatment at intervals after enucleation. The following conclusions have been drawn from the data obtained: (1) Adrenal cortical insufficiency for as long as 2 weeks did not sensitize to the hypertension-inducing property of corticosterone; (2) Corticosterone administration to rats bearing regenerating adrenals, beginning treatment up to 3 weeks after operation, did not enhance the development of hypertension or increase the severity of vascular lesions.