The single item global rating is an economical way of summarizing the state of a person's oral health, and thus is a potentially valuable oral health outcome measure. This research describes the nature, magnitude, and direction of changes in oral health as measured by the global rating with the goal of furthering our understanding of older adults' oral health perceptions over time. Data from a randomized trial of a comprehensive geriatric assessment and prevention program in community-dwelling adults aged 75+ years living in Santa Monica, California, collected between 1988 and 1993 were analyzed. Descriptive techniques as well as a transition matrix were used to examine changes in the global rating and compare these changes to variation, over time, in two relevant measures: the Geriatric Oral Health Assessment Index (GOHAI) and self-reported need for dental treatment. The global rating varied over time and the changes were consistent with those measured by the GOHAI and self-reported treatment need. Whether the change in oral health as measured by the global rating is clinically meaningful, and what specific dental conditions account for these changes remain important topics for future investigation. However, the changes that occur in oral health ratings at the individual level are much more pronounced than the distribution of global rating at each point in time would suggest.