Choosing outcome measures in rehabilitation research depends on the standard research skills of clear thinking, attention to detail, and minimizing the amount of data collected. In rehabilitation, outcome is more difficult to measure because (1) usually several outcomes are relevant, (2) relevant outcomes are affected by multiple factors in addition to treatment, and (3) even good measures rarely reflect the specific interest of any individual patient or member of the rehabilitation team, leading to some dissent. Measurement of general quality of life is not possible because there is little agreement as to the nature of the construct; moreover, measurement of relevant aspects of quality of life would probably give similar results. Cost in terms of resources can be estimated, but there is no validated or even widely accepted method of relating this to benefit in a fair, open, and rational way. Outcome is best measured at the level of behavior (activities), with other measures being used to aid interpretation.