The aim of this study was to analyze the morphological cochlear changes and auditory function observed after the administration of estrogen or progesterone or both. Sixty-two guinea pigs were divided into four groups that received estrogen (group 1), progesterone (group 2), estrogen and progesterone (group 3), and saline solution (controls, group 4), respectively. The auditory evaluation consisted of brainstem evoked response audiometry, performed before and after drug administration. Structural analysis was based on histological hematoxylin and eosin staining preparations. Our results showed changes in latency and amplitude of waves in the study groups that received estrogen or progesterone. The main histological changes observed were inflammatory infiltrate and vacuolization of the stria vascularis. Our results suggest that both estrogen and progesterone lead to morphological and physiological lesions of the cochlea, the degree of the observed lesions depending not only on the presence of these hormones but also on the proportion between them.