Abnormal auditory brainstem responses (ABR) were recorded in 33 of 59 infants with neurological abnormality in the newborn period compared with a 5 per cent incidence in infants who were neurologically optimal. Abnormality of ABR was most common in infants with intraventricular hemorrhage (17/21) but showed no correlation to size of hemorrhage. Abnormal ABRs were also frequent in infants with apnoeic syndrome (5/8) and in infants with abnormal tone patterns in the absence of intraventricular hemorrhage (7/13). All the infants with birth asphyxia had normal ABRs. Although some infants with midbrain signs had abnormal ABRs, the degree of abnormality did not correlate with the severity of clinical signs. ABR may be a useful adjunct in assessing function in neurologically abnormal infants and in confirming early major hearing deficit. Further studies should show whether the abnormal ABR reflects a primary neurological defect or is secondary to recognisable neurological lesions such as intraventricular hemorrhage. Follow-up studies are also needed to establish whether infants who are clinically abnormal and have abnormal ABR will have a worse prognosis than those without associated abnormality in ABR.