Lower socioeconomic status is commonly related to worse health. If poor access to health care were the only explanation, universal access to care should eliminate the association. We studied 14,800 patients with access to Canada's universal health care system who were initially free of cardiac disease, tracking them for at least ten years and seven months. We found that socially disadvantaged patients used health care services more than did their counterparts with higher incomes and education. We also found that service use by people with lower incomes and less education had little impact on their poorer health outcomes, particularly mortality. Countries contemplating national health insurance cannot rely on universal health care to eliminate historical disparities in outcomes suffered by disadvantaged groups. Universal access can only reduce these disparities. Our findings suggest the need to introduce large-scale preventive strategies early in patients' lives to help change unhealthy behavior.