Disability outcomes research: why this supplement, on this topic, at this time?

The objective of this supplement is to define disability outcomes research and to describe the issues facing this new discipline. Drawing on the scientific, English-language literature, this group of articles reviews and comments on the current methods and measures of disability outcomes research, with an eye on providing insights into future directions for disability outcomes research. The future includes expansion of the framework that defined disability and evolution of the methods for the research itself.