The putative goal of sac surgery in Ménière's syndrome is to promote the flow of endolymph from the labyrinth to the endolymphatic sac and thereby relieving hydrops. There are scant published histopathologic data whether sac surgery actually accomplishes this goal.To determine whether sac surgery relieves hydrops by examining the histopathologic changes in temporal bones obtained from individuals who had undergone sac surgery during life for Ménière's syndrome.Temporal bones were examined from 15 patients who had sac surgery. Data on the presence and severity of hydrops, histology of the sac, and whether the procedure relieved vertigo were collected.The surgery failed to expose the sac in 5 cases; 4 of the 5 had relief from vertigo. The sac was exposed, but the shunt failed to reach the lumen of the sac in 8 cases; 4 of the 8 had relief from vertigo. The shunt was successfully placed within the lumen of the sac in 2 cases; both cases failed to experience relief from vertigo. Endolymphatic hydrops was present in all 15 cases.Endolymphatic sac surgery does not relieve hydrops in patients with Ménière's syndrome. Yet, sac surgery relieves vertigo in some patients, but the mechanism of such symptomatic relief remains unknown.