We describe the results of neurological evaluation, magnetic resonance imaging (MRI) of the brain and brainstem auditory evoked response (BAER) testing in 11 chronic toluene vapor abusers. Neurological abnormalities were seen in four of 11 individuals and included cognitive, pyramidal, cerebellar and brainstem findings. MRI of the brain was abnormal in three of 11 individuals and revealed the following abnormalities: 1) Diffuse cerebral, cerebellar, and brainstem atrophy; 2) Loss of differentiation between the gray and white matter throughout the CNS; and 3) Increased periventricular white matter signal intensity on T2 weighted images. BAERs were abnormal (control mean +/- 3 S.D.) in five of 11 individuals. As a group, the latency of V (p less than 0.01), the III-V interpeak (p less than 0.05) and the I-V interpeak latencies were prolonged compared to controls. All three individuals with abnormal MRI scans also had abnormal neurological examinations and BAERs. Two of five individuals with abnormal BAERs, however, had normal neurological examinations and MRI scans. Our data support previous findings of diffuse white matter involvement in chronic toluene abusers and suggest that BAERs may detect early CNS injury from toluene inhalation even at a time when neurological examination and MRI scans are normal. BAERs, therefore, may be a sensitive screening test to monitor individuals at risk from toluene exposure (either abusers or industrially exposed individuals) for early evidence of CNS injury.