Fifty-one children with bacterial meningitis were studied prospectively using serial recordings of brainstem auditory evoked potential (BAEP) from the earliest phase of the disease, according to a standardized protocol. The objectives were to make an early diagnosis and follow the evolution of deafness in the course of meningitis and evaluate the prognostic value of BAEP. Thirty-five children (68.6%) always had normal recordings; 11 children (21.6%) had transient BAEP abnormalities (prolonged wave V latency or elevated threshold for wave I), and five children (9.8%) had persistent pathologic BAEP recordings from the first examination at 48 hours until discharge from the hospital and have a persistent deafness. All recordings that were normal or pathologic at discharge were confirmed by behavioral audiometry 3 months later. These results show the early occurrence of deafness in the course of meningitis with a crucial phase of possible recovery or worsening occurring during the first 2 weeks. There were no cases of "late" deafness or "late" recovery (there was sometimes slight improvement) occurring after discharge; thus BAEPs have a prognostic value. However, observation of a child with clinically proven selective high-frequency postmeningitic deficit but without a hearing handicap, a disorder that was diagnosed early with BAEP (which tests only the high frequencies), is a warning that this method alone is insufficient and that clinical auditory surveillance and conventional audiometry remain necessary.