The purpose of this study was to develop a valid and reliable tool to measure functional change in older persons with moderate to severe dementia. The process was a collaborative one, drawing on the skills of both nurse researchers and clinicians. In Phase I of this study, 20 nursing assistants and 3 licensed nurses volunteered as subjects to develop the new scale. Phase II of the study involved 27 subjects with a known diagnosis of dementia to test the scale's interrater reliability and criterion validity. The results demonstrated significant correlation among the raters and between the instruments. The investigators reported promising results from both the method of using staff expertise in scale development and the scale itself.