The volume of the vestibular aqueduct was studied by a computer-aided volumetric method in 9 temporal bones with endolymphatic hydrops from individuals with Menière's disease (MD), 7 temporal bones with endolymphatic hydrops from individuals without a history of Meniere's disease (non-MD hydrops), and 10 normal temporal bones (controls) to investigate the cause of endolymphatic hydrops in both MD and non-MD hydrops. A hypoplastic vestibular aqueduct was found significantly more often in the MD group than in either the non-MD hydrops group (chi 2-test, chi 2 = 4.063, p less than 0.05) or the control group (chi 2-test, chi 2 = 6.363, p less than 0.05). The difference in volume between the non-MD hydrops group and the control group was not significant. It is speculated that a small vestibular aqueduct (presumably containing a small endolymphatic sac) might be a predisposing factor in Menière's disease. In contrast, in non-MD hydrops, there seems to be no correlation of endolymphatic hydrops with a hypoplastic vestibular aqueduct and endolymphatic sac.