Accurate clinical staging of dementia in older subjects has not previously been achieved despite the use of such methods as psychometric testing, behavioural rating, and various combinations of simpler psychometric and behavioural evaluations. The Clinical Dementia Rating (CRD), a global rating device, was developed for a prospective study of mild senile dementia--Alzheimer type (SDAT). Reliability, validity, and correlational data are discussed. The CRD was found to distinguish unambiguously among older subjects with a wide range of cognitive function, from healthy to severely impaired.