Male rats were exposed to vinyltoluene vapor after pretreatment with polychlorinated biphenyl (PCB). Brain and body solvent burdens were in a linear relationship to the exposure level although it changed between the two weeks while the solvent accumulated in the perirenal fat. The pretreatment caused a significantly smaller burden in the fat samples. Lysosomal acid proteinase was above the control range in the brain homogenate in the highest exposure, while glutathione peroxidase and 2',3'-cyclic nucleotide 3'-phosphohydrolase showed a dose-dependent decrease in the homogenate during the first week. Acid proteinase activity in the glial cells increased above the control range only in the PCB-pretreated rats in the first week. Azoreductase increased in the glial cells above the control range only in the first week, and the pretreatment augmented the increase very significantly. All biochemical effects were largely abolished within two weeks of solvent-free period with the exception of an increase in the cerebral RNA at the highest dose level. Vinyltoluene can cause more pronounced neurochemical effects compared to styrene, xylene, or toluene at similar exposure levels.