In 40 years of development in the area of quality of life, the goal of applicability to the individual patient has not been accomplished. During the 1980s, we strived to improve the applicability of these instruments by refining disease-specific measures and developing patient-specific measures so that the sensitivity of these tools to clinically important change could be increased and comparative indices across conditions could be established. Finding the balance between brevity, reliability, and comprehensiveness will improve practicality. The reliability of serial measurements using the various instruments in individual patients and in small groups of patients needs to be established. In the absence of a gold standard, validity will continue to be derived from testing new measures against accepted clinical measures. The ideal tool for use in clinical practice has not yet been developed. At this time, the clinician may choose among the many reliable and valid questionnaires assessing functional status, health status, and utility, according to his or her purpose. The information gathered from these instruments may help identify patients' problems, set treatment priorities, direct interventions, monitor the longitudinal course of disease, and assist in program evaluation and policy planning.