Summary In the present study, the effects of vitamins E and C on the levels of neuro transmitters and acetylcholinesterase activity in the brains of rats treated with scopo lamine, an inducer of dementia, were examined. Fifty male Sprague-Dawley rats at the age of 5 wk were divided into five groups after 1 wk of adaptation and fed five different diets for 6 wk: a no-scopolamine group, which was a scopolamine-untreated group fed only a basal diet; a scopolamine-treated group fed a basal diet; a vitamin E-supplemented scopolamine treated group; a vitamin C-supplemented scopolamine-treated group; and a vitamins E and C-supplemented scopolamine-treated group. Scopolamine was twice administered by in traperitoneal injection (300mg/kg, body weight), 3 d and 20min prior to sacrifice. Brain acetylcholinesterase activity was markedly reduced by scopolamine injection. However, the supplementation of vitamins E and C in the diet significantly increased the reduced brain acetylcholinesterase activity up to the level of the scopolamine-untreated group. Brain sero tonin concentration in the vitamin C-supplemented scopolamine-treated group was signifi cantly higher than that in the scopolamine-treated group. However, there were no signifi cant differences in brain dopamine and norepinephrine concentrations among all groups. In conclusion, supplementation with vitamin E and/or vitamin C might be useful in main taining brain acetylcholinesterase activity at the normal level and serotonin concentration for some extent under the condition to induce dementia by scopolamine administration.