One hundred ten patients with alcohol dependence and 56 psychiatric patients with either senile dementia, amphetamine psychosis, epilepsy or chronic schizophrenia were investigated with a CT scan of the brain. The maximum width of the 3rd ventricle was measured, and the presence/absence of enlargement of the lateral ventricle and of atrophy of the frontal lobe was determined independently by 3 physicians. The width of the 3rd ventricle in alcoholic and the other patients examined was gradually enlarged with aging, and the width in these patients was significantly larger than that in the age-matched control patients who were selected from the patients with amphetamine psychosis, epilepsy or schizophrenia. The enlargement of the lateral ventricles observed in the alcoholic patients always accompanied the enlargement of the 3rd ventricle, but not vice versa. The alcoholic patients with frontal lobe atrophy showed a higher incidence of withdrawal delirium than the patients without atrophy. These findings suggest that the chronic intake of alcohol might affect primarily the area around the 3rd ventricle, resulting in enlargement of this ventricle and consequential enlargement of the lateral ventricles and also that the alcoholic patients with frontal lobe atrophy could have a high risk for a manifestation of alcoholic withdrawal delirium.