Racial and ethnic health disparities in the processes and outcomes of chronic disease care are pervasive, well documented, and consistently linked to health insurance coverage. Insurance instability (the frequency of switches in insurance coverage or gaps without coverage), may contribute to disparities in outcomes of chronic disease care. With the explicit goal of reducing disparities, Massachusetts (MA) Health Insurance Reform has now extended comprehensive health insurance coverage to 98% of the state's residents, with disproportionately greater gains in coverage among racial/ethnic minorities and the poor. To examine if MA insurance reform has lessened health disparities through increased insurance stability, our specific aims are: Aim 1: To examine changes in insurance instability pre- and post-reform, overall and comparing racial/ethnic specific minority populations to whites. We hypothesize that (a) Insurance instability decreased in the post-reform period and (c) Insurance instability decreased more for racial/ethnic minorities. Aim 2: To examine whether patients receiving care post-insurance reform had better processes of chronic disease management and improved health outcomes, compared with patients receiving care pre-insurance reform, and whether such patterns vary by race/ethnicity. We hypothesize that improvements in processes and outcomes of chronic disease management were greater among racial/ethnic minorities who benefited the most from insurance reform, resulting in reduced disparities. Aim 3: To assess whether patients with more favorable insurance stability had better processes of chronic disease care and improved health outcomes compared to patients with less favorable insurance stability, and whether racial/ethnic minority patients experienced disproportionately greater gains. We hypothesize that greater insurance stability will be associated with improved processes and outcomes of chronic disease management, resulting in reduced disparities. We will conduct an innovative study to assess the processes and outcomes of care for six highly prevalent, chronic conditions before and after the implementation of MA Health Insurance Reform. These conditions are diabetes, hypertension, hyperlipidemia, congestive heart failure, asthma, and chronic obstructive pulmonary disease. We will utilize existing electronic medical records on over 110,000 subjects from Boston Medical Center and eight of its affiliated federally qualified Community Health Centers, the largest safety net institution in New England that serves African American and Hispanic communities, and Tufts Medical Center, which serves a large Asian American community in Boston's Chinatown. When the study is completed, we will provide empiric data on the direct impact of insurance reform and insurance instability on health disparities in multiple populations.