Background:To judge the efficacy of new, putative stroke therapies, we need a method to measure neurological deficit accurately in groups of patients before and after treatment. No single measurement technique has yet proven to be universally acceptable, but one approach is the use of rating instruments that summarize the neurological deficit found on clinical examination. Currently, stroke assessment scales may be based on the examination of physical deficits, an inventory of activities of daily living, or a global evaluation of functional outcome.Summary of Review: Scientific methods for authenticating stroke scales are available in the psychometric and statistical literature. We review currently available stroke scales for their validity and reliability and propose investigations needed to refine further the standardized measurement of neurological deficit following stroke.Conclusions: We suggest that clinical stroke trials include a physical deficit scale and a global rating during the acute phase and that an activities of daily living scale be added at later points in recovery. (Stroke 1991;22:1345-1352)