The Social Security Administration (SSA) is reengineering its disability claims process for providing cash benefits and medical assistance to blind and disabled persons under the Social Security Disability Insurance (SSDI) program and the Supplemental Security Income (SSI) Program (Title II and Title XVI of the Social Security Act). As one element of this effort, SSA has proposed a redesigned disability determination process. The agency has undertaken a multi-year research effort to develop and test the feasibility, validity, reliability, and practicality of the redesigned disability determination process before making any decision about implementing it nationally. SSA requested the National Academy of Sciences to review and provide advice on its research relating to the development of a revised disability decision process, including the approach, survey design, and content of the Disability Evaluation Study (DES). One of the committee's tasks is to examine SSA's research into existing and other developing functional assessment instruments for the redesign efforts and to provide advice for adopting or developing instruments for the redesigned decision process and the DES.