Arthritis is a leading cause of work-related disability and the leading cause of disability among persons aged greater than or equal to 65 years in the United States. However, there are few national or state-specific estimates and no projections of arthritis prevalence or its impact. To develop national and state estimates of arthritis prevalence and physical activity limitation for 1990 and to project these measures through 2020, rates derived from household interview data from the 1989-1991 National Health Interview Survey (NHIS) were applied to the 1990 census population and to census population projections. This report presents the results of that analysis.