We describe the findings of magnetic resonance imaging (MRI) of the brain in 6 chronic toluene vapor abusers and the neuropathological findings in 1 abuser not studied by MRI. MRI in 6 chronic toluene abusers revealed the following abnormalities: (1) diffuse cerebral, cerebellar, and brainstem atrophy; (2) loss of differentiation between the gray and white matter throughout the central nervous system; and (3) increased periventricular white matter signal intensity on T2-weighted images. Another chronic toluene abuser (MRI not performed) died as a result of acute toluene overdose. The brain displayed diffuse, ill-defined myelin pallor, maximal in cerebellar, periventricular, and deep cerebral white matter. Neurons were preserved throughout, axonal swelling or beading was not seen, gliosis was minimal, and occasional, scant perivascular macrophage collections were seen. Taken in concert, these findings suggest that the pathological and MRI abnormalities are due to either increased water content of the white matter or subtle toluene-induced metabolic changes in myelin.