Functional status measurement and the assessment of health status are reaching their maturity as technical disciplines. Good tools exist that meet requirements such as brevity, validity, reliability, ease of administration, and ease of scoring, which make them potentially suitable for use in clinical practice. Despite this progress, widespread adoption of measurement tools has not occurred in the clinical world. The authors analyze both the potential and the barriers to use of health assessment tools in practice and note the need for better scientific evidence of their clinical utility, as opposed to their information content. Dissemination of these tools among practitioners will require, above all, evidence and conviction that the use of measurement instruments will actually enhance the very health status outcomes they assess.