The project was designed to investigate sources of available data on the incidence, prevalence, diagnostic conditions, functional limitations, and activity restrictions of the disabled population in the United States, and to design a comprehensive data system. Difficulties, both conceptual and practical in estimating incidence and prevalence are cited, including divergent data sources, varying definitions of disability and handicap, and inconsistent methodologies. Guidelines for extrapolating from existing data are given, including techniques of aggregation and merging, and linking files by entering distributions and summary figures into multidimensional tables. The report recommends steps to be taken by the National Institute of Handicapped Research to improve disability statistics, including advocacy for a uniform functional definition of disability and handicap and for inclusion of disability data in census and other national surveys. The development of a Disability Data Archiving and Analysis Center is detailed, and such a project's activities in nine categories are described: acquisition, cataloging, abstracting, reference, circulation, file processing, analysis, dissemination, and data improvement. Functional components as well as procedures, examples of user requests, and administration considerations are noted. Among five appendixes are papers on machine readable data files and a selected bibliography on the definition of measurement and disability. (CL)