This article summarizes personal views on the rapidly evolving field of functional health assessment and comments on their implications for advances in assessment methods used in rehabilitation medicine. Topics of strategic importance included (1). a new formulation of the structure of health status designed to distinguish role participation from the physical and mental components of health for purposes of international studies; (2). applications of item response theory that offer advantages in constructing better functional health measures and cross-calibrating their underlying metrics; (3). computerized dynamic assessment technology, well proven in education and psychology, which may lead to more practical assessments and more precise score estimates across a wide range of functional health levels; and (4). intellectual property issues involved in standardizing and promoting readily available assessment tools, ensuring their scientific validity, and achieving the best possible partnership between the scientific community and those developing commercial applications. Promising results from preliminary attempts to standardize and improve the metrics of functional health assessment constitute grounds for optimism regarding their potential usefulness in rehabilitation medicine. Someday, all tools used to measure each functional health concept, including the best single-item measure and the most precise computerized dynamic health assessment, will be scored on the same metric and their results will be directly comparable. To achieve this goal in rehabilitation medicine, we have much work to do.