In all the cases of profound deafness that we examined, the sensory epithelium along the basilar membrane had severely degenerated. However, ganglion cell counts and peripheral fiber estimates demonstrated a high degree of variability when analyzed with respect to the state of the organ of Corti or the etiology of the original cochlear disorder. We conclude that a complex interplay of factors determines the number of cells remaining in the spiral ganglion at a given time. It appears impossible at present to predict which diseases or toxic states produce primarily a sensory loss while leaving a uniform and adequate number of cochlear neurons functionally intact. We would like to emphasize that although the ganglion cell counts were consistently reduced in all our cases of profound sensorineural deafness, it has always been a surprise to us to find that the actual numbers of surviving cells are considerable. Of 15 patients, all of whom were totally deaf, only 3 had ganglion cell counts less than 10,000, whereas the majority had counts well above 15,000. Observations of this kind are possible only if accurate ganglion cell counts are carried out. Estimating the number of spiral ganglion cells by only looking at microscopic sections usually results in estimates of greater cell loss than is actually present.