the functional integrity of the peripheral auditory system in the gunn rat was examined. the gunn rat is a mutant of the wistar strain with congenital deficiency of the liver enzyme uridine diphosphoglucuronyl transferase which is essential for bilirubin conjugation. this deficiency is inherited as an autosomal recessive trait with the homozygous animals (jj) showing evidence of bilirubin encephalopathy. the heterozygotes (jj) have 50 percent enzyme deficiency and are not jaundiced. the long-evans rat served as a control. the approach was to study the discharge characteristics of single auditory nerve fibers using standard procedures in a closed and calibrated sound system. various response measurements which would reveal pathological processes in the cochlea were analyzed. in this study, spontaneous discharge rate distribution and interspike interval statistics derived from gunn rate auditory nerve recording were found to be within the normal range, and cochlear nerve histology showed no evidence of neuropathy