In the present study, we tested whether lead intoxication induces change of the thiamine content and the seizure threshold in rats and the changes of seizure threshold are related to the changes of thiamine status. It was also tested whether administration of excessive thiamine could reverse the toxic manifestation of lead in rats. Four groups of Wistar rats were prepared: 1) control group, 2) lead treated group, 3) lead plusthiamine treated group, and 4) thiamine deficient group. Each group of animals was divided into three subgroups based on age: 3, 7 and 16 weeks. In each group, thresholds of electroshock seizure and thiamine contents in brain regions including telencephalon, brain stem, cerebellum were measured. Thiamine contents in brain regions of the lead treated group were significantly lower than those of the control group and thiamine treatment reversed the decrease back to the control level. Thresholds of the electroshock seizure of the lead treated group in 3, 7 week old rats and those of thiamine deficient group in 3 week old rats were significantly lower than those of the control group. These observations were reversed by the supplementation with thiamine. These results from the present study suggest that increased seizure sensitivity induced by lead intoxication in rats may be mediated at least in part through the changes of thiamine status.