The etiopathogenesis of Meniere's disease has remained controversial since the early 1900s. Many investigators have studied the molecular and cellular pathology of the inner ear in patients with this disorder. Three basic pathologic mechanisms have emerged; fibrosis of the endolymphatic sac and vestibular epithelia, altered glycoprotein metabolism, and immune-mediated inner ear disease. This article reviews the current understanding of these three basic pathologic processes.