Brainstem auditory evoked potentials (BAEPs) were recorded from 55 patients with postconcussion syndrome (PCS) to elicit evidence of an organic and subclinical brainstem disorder. Fifteen patients (27.3%) showed abnormal responses unilaterally or bilaterally, especially for one or more interpeak latencies prolonged beyond the upper 99% confidence limits. Other 9 patients had borderline responses. The BAEP alterations were not correlated either with dizziness at the time of recording, or with vestibular troubles in the routine caloric test. Though BAEP abnormalities may be present a long time after injury, we found an improvement of responses in the majority of 14 re-tested patients. These data show that BAEP can give an objective demonstration of a reversible brainstem disorder in patients with PCS.