This study evaluated the electrochemical potentials and potassium concentration (C(K+)) profiles in the perilymph, endolymph, marginal cells, and spiral ligament of adrenalectomized rats in which endogenous corticosteroids had been removed. Electrochemical potentials recorded at the four cochlear sites were not affected by adrenalectomy (ADX). C(K+) was greater in the endolymph of the ADX animals as compared to control animals. Additionally, there was an increase of C(K+) in the marginal cells, perilymph, and spiral ligament tissues of the ADX animals as compared to control animals, although the observed increases were not statistically significant. In a previous study (Ma et al., 1995a), it was found that potassium levels in the blood plasma of ADX animals were higher than those identified in normal rats; thus, ADX may have a systemic effect on C(K+) that is detectable in both tissues and fluids within the cochlea. Even though C(K+) was elevated within the cochlea in the ADX model, the functional response of the inner ear, as assessed electrophysiologically, was not altered.