Accurate, efficient measurement of disease status has become a key issue in MS clinical practice and research. Despite some perceived problems, the Expanded Disability Status Scale (EDSS) remains the most widely used comprehensive measure of impairment. There is also a place for more restricted scales of impairment which focus on some aspects of neurological function in more detail than the EDSS e.g. measures of ambulation, arm function and cognitive function. Improvements in scales of impairment in the future is likely to result from the use of more quantitative tests of selected components of the neurological examination.