Since 1979, when McCabe first described a pattern of bilateral sensorineural hearing loss (SNHL) characterized by a rapid progression over days to weeks, the postulated autoimmune basis of this disease remains unknown. Various attempts have been made to develop the best assays that will clinically confirm the diagnosis and will help identify those patients who may respond to immunosuppressive therapy. The Western blot assay has now been widely applied by different research groups. It has been suggested that antibody to the 68-kD protein is most closely associated with this disorder. Recent analyses suggest that the protein of interest is probably a heatshock protein (hsp 70) with this molecular weight. This disease pattern of rapidly progressive bilateral SNHL presents itself clinically as a different disease than endolymphatic hydrops with fluctuating SNHL, and it is most often associated with vertigo and roaring tinnitus. Meniere's disease may be also immune-mediated, but lacks an autoimmune basis. Its etiopathogenesis is different. A critical review of our own Western blot analyses from patients with either idiopathic rapidly progressive SNHL (N = 33), sudden deafness (N = 53), or other SNHL forms (N = 71) is presented. Immuno-suppressive treatment responses were evaluated. A new concept of immune-mediated endolymphatic hydrops was also further developed on the basis of recent experimental data and earlier clinical observations in order to focus on another aspect of this most intriguing inner-ear disease.