Trimethyltin (TMT) has been shown to produce damage in the limbic system and several other brain areas. To date, damage to sensory systems has not been reported. The present study investigated the integrity of the visual system following acute exposure to TMT. Rats were chronically implanted with electrodes for recording the evoked response from either the visual cortex or optic tract following photic stimulation. Following recovery, the animals were exposed to either 0 (saline), 4, 5, 6, or 7 mg/kg trimethyltin chloride (TMT). Evoked potentials were averaged and peak-to-peak amplitudes and latencies were determined. The results indicated that exposure to TMT produces alterations in the visual evoked response. The pattern changes suggested two effects, an alteration in tetinal processing and an alteration in arousal. The manifestation of these changes was an increase in early peak latencies recorded from the visual cortex and the optic tract, a decreased amplitude recorded from the visual cortex and optic tract early peaks (all suggestive of retinal changes) and a decreased P3N3 amplitude and N3 latency recorded from the visual cortex (suggestive of increased arousal). The results demonstrate that TMT does produce alterations in sensory systems as well as in the limbic system.