The reliability, validity, and sensitivity to change of the Hierarchic Dementia Scale (HDS) were tested in two cross-sectional studies and one longitudinal study. Results prove the HDS to be a simple-to-conduct method, economical in terms of time, and possessing high reliability and high concurrent and criterion-related validity. The HDS appears capable of use at all stages of dementia and capable of permitting studies of the course well into the advanced stages of the illness.