MARKED hearing loss associated with Cogan's syndrome is in itself a rare enough entity to warrant reporting. The marked improvement, however, in the cochlear function in a case following the oral use of hyperosmotic glycerin suggested the present writing in the hope that the trial of this agent by others may lead to proper evaluation of its efficacy. In 1945 Cogan1 reported four cases of "non-syphilitic interstitial keratitis associated with vestibulo-auditory symptoms." Although the more than 40 cases reported in the literature have been predominantly in young adults, cases have been reported of patients from age 2½ to 60 years. Clinically, the syndrome is that of a nonspecific keratitis, either unilateral or bilateral, accompanied or followed by profound disturbances in vestibular and auditory functions. It tends to take a chronic course with multiple unpredictable recurrences. Its etiology remains a puzzle. Serrins et al2 relate cases associated with smallpox