Seventeen patients with clinically diagnosed Alzheimer's disease and 13 healthy age-matched controls were studied by means of computed tomography (CT). To assess cerebral atrophy, regional volumetric measurements and parenchymal density measurements were performed. The results indicate that: (1) Alzheimer patients show diffuse cerebral atrophy in the early stage; (2) the evaluation of lobar atrophy by means of CT is useful for the clinical diagnosis of Alzheimer's disease; (3) the evaluation of parenchymal density by means of CT is not as sensitive as the evaluation of lobar atrophy.