Methods: Between 1998 and 2006, we enrolled and assigned 105 intractable Meniere's patients to examine plasma vasopressin during remission of vertigo attacks (controls: 30 patients with chronic otitis media). Using the real-time PCR method, we examined V2R mRNA expression in the endolymphatic sac in 12 patients (controls: 6 patients with acoustic neurinoma). By means of cell culture and cyclic AMP assay, we also examined cyclic AMP activity in the endolymphatic sac in 3 patients (controls: 3 patients with acoustic neurinoma).