The magnitude and quality of the problem of disability for the United States elderly population was analyzed in a series of projections. An analysis of the impact of disability on this population is more difficult than for other disabled groups because previously, in both the popular and scientific literature, there was the assumption that the prevalence and severity of disability was a natural consequence of the aging process. Such a perspective has implications not only for initiatives to improve the health and functional states of the elderly population but also for the perception of the level of disability, the handicaps associated with it, and the types of services that are appropriately provided. This image of the natural emergence of frailty with age is now challenged by a number of studies. The extreme heterogeneity of functional status in even the oldest-old (those aged 85 and over) population is evidence that functional impairment among the elderly is not a natural consequence of aging and must be evaluated on an individual basis. There is also increasing evidence that the physiological processes generating impairment are subject to intervention and, in some cases, may even be partly reversed and function regained. Recent research has begun to identify the risk factors for such processes and to explicate the mechanisms of these processes so that more effective interventions can be developed. Whatever interventions may be introduced, the demographic aging of the population will cause large increases in the number of disabled elderly. This is a national problem whose magnitude will depend upon the degree to which the broadly defined needs of this population are or are not met. We considered needs on a number of levels. In terms of basic self-care only bathing and toileting are reported as currently "unmet" to a considerable degree. The most serious deficiencies on a relative basis were for physical equipment and changes in the built environment. All of these factors contribute to a general assessment of changes in the size, structure, and needs of the disabled elderly population. It is clear that no single response will suffice given the magnitude of the problems. Thus, a multidimensional approach involving the private sector and state and federal programs, and their coordination, will be needed to develop adequate responses to the problem.(ABSTRACT TRUNCATED AT 400 WORDS)