• Brain-stem auditory evoked responses (BAER) were recorded in a group of 83 patients with a diagnosis of clinically definite or probable multiple sclerosis to assess the relevance of recording contralateral responses simultaneously with ipsilateral responses and to correlate patients disability with the detection of abnormalities. The contralateral responses generally mirrored the ipsilateral responses, but in seven patients the responses differed, mainly involving the presence or absence of wave V. However, contralateral recordings did not contribute significantly to the sensitivity of lesion detection, and their main value was to aid in the recognition of waves when they were not clearly seen in the ipsilateral recordings. The BAER abnormality rates were found to be significantly correlated with disability, and it is suggested that this is an important variable to consider when undertaking or comparing results of BAER studies in patients with multiple sclerosis.