Forty-seven patients with chronic progressive multiple sclerosis were examined to assess the possible relationship between cerebral atrophy (by computed tomography [CT] ) and performance on neuropsychological tests of memory and verbal intelligence. Nineteen patients were found to have mildly dilated ventricles and another nine patients had moderate to severe ventricular enlargement. Performance on memory and intelligence testing was related to the degree of ventriculomegaly. Three linear CT measurements were also recorded. Using this method, the width of the third ventricle proved to be the best indicator of intellectual and memory dysfunction. Measures of cognition and ventricular size did not correlate with length of illness or overall disability as rated by the Kurtzke Disability Status Score.