This research plan describes a framework for defining and developing the field of rehabilitation sciences and research opportunities for the National Center for Medical Rehabilitation Research (NCMRR) and other agencies funding medical rehabilitation research. The plan addresses the needs of both persons who are involved in habilitation and in rehabilitation. Following an introduction and a historical perspective, the scope of disability is discussed, including prevention, epidemiology, and demography. A conceptual model of the rehabilitation process is presented which builds on the strengths of existing scientific principles and social values. The focus is on the person with a disability and how that person adapts to functional limitations in his or her family, work, and local community. The model provides for five overlapping domains of research, including pathophysiology, impairment, functional limitation, disability, and societal limitation. Terminology in disability classification and issues in medical rehabilitation research are discussed. Future directions for the field and research initiatives and opportunities are discussed, focusing on the areas of mobility; behavioral adaptation; whole body system response; assistive technologies; measurement, assessment, and epidemiology; treatment effectiveness; and the training of research scientists. Progress of the NCMRR in supporting research initiatives and coordinating research is cited. Appendixes describe research activities, authorizing legislation, and assistance mechanisms used to support research. (JDD)