Book excerpt: The Social Security Administration (SSA) is engaged in redesigning its disability determination 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). The agency has undertaken a multiyear research effort to develop and test the feasibility, validity, reliability, and practicality of the redesigned disability determination process before making any decision about its national implementation. Survey Measurement of Work Disability reviews and provides advice on this research. One of the major areas for review is the ongoing independent, scientific review of the scope of work, design, and content of the Disability Evaluation Study (DES) and the conduct of the study by the chosen survey contractor. This report identifies statistical design, methodological, and content concerns and addresses other issues as they arise.