Abstract
The human endolymphatic sac was analysed electron microscopically in patients undergoing acoustic Schwannoma surgery or vestibular nerve section. In addition, endolymphatic sacs from cadavers were analysed light microscopically. The results show that the human sac is endowed with a variable number of leucocytes and that there is a continuous recirculation of immunocompetent cells in this area of the inner ear that may be of importance for clearance of the inner ear from foreign substances and microorganisms derived from nearby located infection-prone areas. The possibility in Meniere's disease of a disturbed immunological activity in the sac is discussed.