TMT is a neurotoxicant known to alter auditory function. The study was designed to compare TMT-induced auditory dysfunction using behavioral, electrophysiological, and anatomical techniques. Adult male Long Evans hooded rats (n=9-12/group) were acutely exposed to saline, 3, 5, or 7 mg/kg TMT. Auditory thresholds were determined 11 weeks post-dosing for 5 and 40 kHz tones using reflex modification of the auditory startle response (ASR). Brainstem auditory evoked response (BAER) thresholds were determined for 5, 40, and 80 kHz tonal stimuli 9 weeks post-dosing. Cochlear histology was assessed at 13 weeks post-dosing. Functional endpoints demonstrated a high-frequency hearing loss. ASR thresholds for 40 kHz tones were elevated 25-35 dB in all dosage groups. BAER thresholds for 40 and 80 kHz tones were elevated 30-50 dB in the 5 and 7 mg/kg groups. Organ of Corti surface preparations revealed a pattern of damage suggesting classical ototoxicity. These data demonstrate the utility of the ASR and BAER in detecting functional alterations in audition and indicate that TMT-induced high-frequency hearing loss is associated with cochlear damage. (Copyright (c) 1990 by Academic Press, Inc.)