There have been many reports regarding morphologic and biochemical changes of inner ear tissues by adrenocorticosteroid hormones, but the exact mechanism and their regulation of such inner ear activity still remain an enigma. Clinically, certain inner ear disorders, eg, sudden sensorineural hearing loss, vestibular disturbances and Meniere's disease, are seemed to be associated in patients with adrenocortical imbalances, and such imbalances are responded well to whole adrenocortical extraction by unknown exact mechanism. So authors examined the effect of adrenocorticosteroid hormones on the cellular integrity of marginal cells and morphologic variation of stria vascularis of cochlear duct after bilateral adrenalectomy in rats, and obtained the following results. 1) Aldosterone level in serum was significantly decreased in adrenalectomized rats (p<0.05). 2) No specific findings except mild increase in intercellular space of stria vascularis were seen after adrenalectomy in rats by light microscopy. 3) Electronmicroscopic changes after adrenalectomy in stria vascularis were swollen marginal and intermediate cells with lower density in marginal cells compared with controls, and variant sized intracytoplasmic vacuoles were seen with intercellular edema. According to the results we obtained, adrenocorticosteroid hormones affect the cellular integrity and morphology of stria vascularis of cochlear duct. These might result in the alteration of the enzyme activity of the inner ear and play a major role in microhomeostasis of inner ear including regulation of endolymph and ion transport.