Borderline personality disorder is an increasingly recognized condition and frequent management problem in psychiatric and nonpsychiatric practice. Paroxysmal changes in affect and behavior, high incidence of soft neurologic signs and frequent EEG alterations, and evidence of clinical response to antiepileptic drugs have suggested cerebral dysfunction, particularly involving the limbic system or reticular activating system. We recorded early latency brainstem auditory evoked potentials (BAEPs) and long-latency auditory event-related potentials (ERPs) in 20 patients fulfilling DSM-III-R criteria for this disorder. BAEPs were recorded from Cz to ipsilateral and contralateral ear reference, with rarefaction clicks presented at 11.1 per second and 70 dB SL. Two thousand averages were recorded and replicated for each ear, with filter band pass of 150-3000 Hz and 10 ms analysis time. ERPs utilized binaural stimulation with 1000 and 3000 Hz tones in an 80:20 ratio, with interstimulus interval 1.1 second, analysis time 1000 ms, and filter band pass 1-100 Hz. Two hundred averages were recorded and replicated from Cz with linked ear reference. No differences were evident in I-III, III-V, and I-V interpeak latencies between borderline patients and age-matched neurologically and audiologically normal controls. N1, P2, and N2 components of the AEPs were longer in latency and lower in amplitude in borderline patients, while P3 latency was longer and amplitude was attenuated in borderline patients as compared to controls. These findings may suggest differences from normals in attention maintenance and in limbic system function.