The purpose of this report is to present a review of the clinical and histopathologic findings in human cytomegalovirus (HCMV) labyrinthitis. Human cytomegalovirus infection was first recognized in its congenital disseminated form and, subsequently, in a subclinical form. In 1968, the first temporal bone demonstration of endolabyrinthine infection was reported. To date, there have been reports made on only nine temporal bones in infants with HCMV infection. The light microscopic findings, in general, have been similar, with cytomegalovirus inclusion-bearing cells involving the nonneuroepithelial cells in both the cochlear and vestibular endolabyrinth. A few cases have been studied with fluorescent antibody methods, but have resulted in conflicting reports regarding the presence of virus in cells of the organ of Corti and spiral ganglia. Subclinical congenital HCMV infection, including labyrinthine infection, has also been studied. Only two groups have performed major prospective studies along with systematic and careful periodic audiologic evaluation in cytomegalovirus congenitally infected children. Their findings demonstrated significant hearing loss in 33% to 48% of symptomatic patients and in 6.9% to 13% of asymptomatic children. There also was evidence of progressive hearing loss in some of these children. Vestibular dysfunction is less well characterized. The long-term sequelae may include Meniere's syndrome. Acquired HCMV infection in children and adults has not been demonstrated histopathologically, although it has been associated with sudden deafness and acute labyrinthitis. This observation is based primarily on serologic data.