Brain computed tomographic scans of 60 patients with early-onset Alzheimer's disease (mean age, 60.7 years) were compared with those of age- and sex-matched control subjects. Computed tomographic analysis included standard ventricular measurements as well as subjective ratings of ventricular and sulcal size. These indices were correlated with the results of a battery of neuropsychological tests and electroencephalographic findings. Linear measurements of ventricular size were significantly greater in the patients with Alzheimer's disease than in the age-matched control group (p less than 0.0005). Using subjective appraisal of ventricular and sulcal size, the neuroradiologist noted abnormalities significantly more often in patients than in controls (p less than 0.0005). Linear measurements of ventricular size correlated significantly (p less than 0.05) with the severity of aphasia and dementia and the presence of electroencephalographic abnormalities. There was, however, no correlation between the subjective judgment of cortical atrophy and the degree of impairment as measured by neuropsychological tests. The findings in this study demonstrate the usefulness of computed tomographic imaging in Alzheimer's disease of early onset.