Long-Evans hooded rats were exposed to single doses of toluene (p.o.) at 0, 250, 500 and 1000 mg/kg, to p-xylene (p.o.) at 0, 125, 250, 500, 1000 and 2000 mg/kg, and to inhalation of p-xylene for 4 hrs at 0, 800 or 1600 ppm. The functional integrity of the visual system was evaluated using flash-evoked potentials (FEPs). The data indicated a significant depression in amplitude of FEP peak N3 at 250 mg/kg and higher dosages of toluene and p-xylene. A similar depression in peak N3 amplitude was observed following inhalation exposure to 1600 ppm p-xylene. The effects produced by oral administration of 500 mg/kg p-xylene or toluene lasted at least 8 hr, while the effect of inhaled p-xylene dissipated within 75 min of removal from the exposure. FEP peak N3 is presumed to be related to arousal, such that increase in arousal from a relaxed state should decrease amplitude. Rats administered amphetamine in dosages of .6, 1.2 and 2.5 mg/kg (known to increase arousal) also had reduced N3 amplitude. The effects of p-xylene and toluene on FEPs, while indicative of altered processing of visual information, may be secondary to changes in arousal or excitability.