In the first portion of this study, the effects of two levels of contralateral masking on the auditory brainstem response (ABR) were investigated in 10 normal-hearing subjects. No significant changes were observed in the mean latency-intensity functions or the mean amplitude-intensity functions of this group of subjects when noise of various levels was added to the nontest ear. In the second portion of this study, ABRs were also recorded from the poorer ear of four subjects with a profound unilateral sensorineural hearing loss. Results from the latter group revealed a crossed-over wave V in all cases when the stimulus was delivered to the poorer ear and the nontest (better) ear was not masked. Contralateral masking obliterated this "crossed ABR" in all four unilaterally impaired subjects. These results provide support for the use of contralateral masking when recording from the poorer ear of subjects having asymmetrical hearing loss.