The amplitude of wave V of the auditory brainstem response (ABR) has been found to vary in a manner consistent with the psychophysical critical band data. When the frequency separations between members of a tone pair, displaced symmetrically around some center frequency, exceed some critical value, the amplitude of wave V undergoes an abrupt increase. Specifically, tonal pairs straddling 2 and 4 kHz were studied; abrupt increases in wave V amplitude were generally seen when frequency separations were between 600 and 800 Hz for a center frequency of 4 kHz, and between 200–400 Hz for a 2‐kHz center frequency. These electrophysiologically derived estimates are in reasonable agreement with psychophysical values found in the literature.