Auditory brainstem responses and simultaneous transtympanic electrocochleographies were investigated in 92 subjects aged between 50 and 89 years with normal hearing or mild presbycusis. Subjects were classified into four age-related groups: 16 subjects in the sixth decade, 28 in the seventh decade, 32 in the eighth decade and 16 in the ninth decade. Thirty young subjects with normal hearing aged 20–29 years were chosen as controls. The result showed progressive delay of wave I (or action potential: AP), wave III and wave V and lengthening of the interpeak intervals (IPIs) of waves III-V and I-V in the subjects aged 50-79 years. In the subjects in the ninth decade, shortening of IPIs of waves I–III and I–V was noted in spite of further delays of wave I. The amplitude of APs on electrocochleography decreased in the groups with mild presbycusis. Both the lengthening and shortening of IPIs might be electrophysiological alterations occurring with aging in the central auditory pathways.