It is difficult to objectively and comprehensively measure the effects of the rheumatic diseases or their treatment. The concept of patient outcome measurement now encompasses many components: physical health, mental health, everyday functioning, general perceptions of well-being, treatment side effects, and cost-versus-benefit. Accordingly, a major research effort has been directed toward developing methods for the measurement of health status and patient outcome in arthritis and other rheumatologic diseases. The intent of this effort is to produce standard measures for evaluating disease impact, treatment impact, and costs of care. Numerous questionnaire-based instruments have appeared for clinical researchers to use, but they are couched in unfamiliar jargon and use terms such as "indirect costs," "lost productivity," and "quality-of-life." As these articles appear in the literature and clinical investigators include such measures in their studies or clinical trials, a review of the terms and an evaluation of these measures appears timely. This report describes the present state of the art, emerging problems, and future directions.