The potential neuroprotective/cognitive enhancing actions of captopril were investigated in the trimethyltin (TMT)-induced neurotoxicity rat model. Acute exposure to TMT produces alterations in locomotor activity, passive avoidance behaviour and spatial memory tasks. Captopril treatment given in combination with the single acute injection of TMT reversed the deficits in spatial memory tasks in 8 out of 25 trials. While post-treatment of TMT-treated rats with captopril brought about a significant improvement in 3 out of 25 trials, pre-treatment of rats for 3 weeks with captopril did not reverse the behavioural deficits produced by TMT in the Morris maze test. Captopril treatment did not block the characteristic hyperactivity or the deficits in passive avoidance behaviour of TMT-treated animals.