Vestibular sensory organs were examined ultrastructurally in two cases of delayed endolymphatic hydrops. The patients, two women, 27 and 16 years of age, suffered profound sensory hearing loss in childhood and experienced severe, recurrent vertigo. Specimens were obtained by a translabyrinthial vestibular nerve transection. We studied the utricular macula and the lateral and posterior cristae in one case, and the utricular macula, the anterior and posterior cristae, and the vestibular ganglion in the other. The otoconia and the otoconial membrane, the sensory epithelia, and the vestibular ganglion appeared fairly normal. Although the entire vestibular end organs were not studied in these cases, it was surprising that the ultrastructural findings did not conclusively identify vestibular end organ pathology as the cause of the vertigo attacks.