The characteristics of Reissner's membrane from 47 human cochleae with mild endolymphatic hydrops, profound sensorineural deafness and normal ears were studied by light microscopy. The highest cell densities were observed in the zones adjacent to the limbus spiralis and the stria vascularis. The cell density of Reissner's in normal ears decreased with age concomitant with an increased formation of epithelial cell clusters. In hydrops, the density increased with the exception of the apical turn. However, sporadic loss of the cells in isolated areas of the membrane was observed. The ears with profound deafness showed no significant changes compared with age-related controls. No definite relationship between Reissner's cell density and hair cell loss or strial atrophy was observed.