We examine the roles that insurance coverage, the delivery system, and external factors play in explaining persistent disparities in access among racial and ethnic groups of all ages. Using data from the 1996-1999 Medical Expenditure Panel Surveys and regression-based decomposition methods, we find that our measures of health care system capacity explain little and that while insurance clearly matters, external factors are equally important. Employment, job characteristics, and marital status are key determinants of disparities in access to insurance but are difficult for health policy to affect directly. Much of existing disparities remains unexplained, presenting a challenge to developing policies to eliminate them.