Averaged auditory-evoked vertex responses were obtained from eight normal-hearing female subjects in response to 32 monaural 1000-Hz tone bursts at 30 randomly presented combinations of recovery period (interstimulus interval) and stimulus intensity (sensation level). From curves describing N1−P2 peak-to-peak amplitudes, an equation was derived that describes the combined effects of recovery period and stimulus intensity on evoked response amplitude. The results showed evoked response peak-to-peak amplitude to be a dual function of both recovery period and stimulus intensity. At a given stimulus intensity, evoked response amplitude was a logarithmic function of recovery period. At a given recovery period, evoked response amplitude was a power function of stimulus intensity. The combined effects of recovery period and stimulus intensity produced equal ratio changes in the slope and the intercept of the recovery function with equal ratio changes in stimulus intensity.