Contralateral masking is often recommended in auditory brainstem response (ABR) testing in order to reduce or eliminate the participation of the nontest ear. The present study evaluates the effects of contralateral sound on the ABR. Vertex‐mastoid recordings were made on a total of 30 young‐adult subjects with normal heating. Stimulus paradigms employed a 4‐kHz probe and a contralateral continuous tone or a contralateral forward masker. Both the continuous‐tone and forward‐masking experiments resulted in statistically significant amplitude changes in the probe‐evoked ABR. Waves III and VI, averaged across experiments, conditions, and subjects, showed a 28.7% increase in amplitude in the presence of a contralateral stimulus. In contrast, the amplitude of wave V, averaged across experiments, conditions, and subjects, was reduced by 11.2%. Latency measures for all waves often showed a slight, but statistically significant, increase. In regard to the enhancement of wave III by contralateral sound, we speculate that the descending auditory system is involved. The amplitude changes obtained for waves III, V, and VI contrast strongly with earlier results on ipsilateral masking.