This paper presents the findings of an epidemiological analysis of disability among adults in the noninstitutionalized continental United States population. Data were collected through interviews with a probability sample of persons 18 and over, yielding 6,493 completed schedules comprising 80.3 percent of the sample. Distinctions were made among concepts and indicators of pathology, impairment, individual performance, and social performance. Central to the analysis were two dimensions of individual performance (physical and emotional) and two dimensions of disability in social performance (work and independent living). A number of socio-demographic characteristics were included in the analysis. The results show the relative contributions of pathology and impairment to performance on the individual level, and the relative contributions of all of these factors on social performance, that is, the two dimensions of disability. Through pathology, impairment, performance at the individual level, and the socio-demographic characteristics, it was possible to account for 38 percent of the variance in work disability and 74 percent of dependence-independence in community living. Further explanations are given for variance in work disability. Estimates of the size of populations reporting varying types and severities of disability are also presented.