Fourteen of 100 unselected patients in an intensive care nursery were found by the auditory brainstem evoked response (ABR) method to suffer significant hearing loss; of these 8 were ultimately discharged home. Analysis of the 100 clinical records identified 9 risk factors of which most, like low Apgar scores, are already known (Table I). However, neonatal asphyxia appeared to be associated with hearing loss only when repeated episodes of acidosis accompanied it (Table III). We conclude that the ABR readily identifies the hard-of-hearing premature and estimates the type and amount of his peripheral hearing loss, and that physiological events associated with prolonged perfusion of the cochlea with blood low in pH may be the most common cause of hearing disorder in this group.