The total protein levels in the perilymph of patients with acoustic neuromas, meningiomas, and Meniere's disease are contrasted. All specimens were obtained from the lateral semicircular canal during removal of the bony labyrinth. Any specimens with significant contamination by hemoglobin or serum proteins, as judged by the presence of hemoglobin/haptoglobin complexes, were discarded from this study. The findings of greatly increased perilymph protein levels in the tumor groups confirmed the reports of other workers. The levels in the Meniere's disease group compared favorably with the normal protein levels in perilymph. A very significant (p Less Than 0.05) difference between the acoustic neuroma group and the meningioma group is noted. This difference is probably tumor related, because in all cases of both groups, tumor entered and filled the internal auditory meatus.