About 28 million Americans are currently uninsured, and millions more could lose coverage under policy reforms proposed in Congress. At the same time, a growing number of policy leaders have called for going beyond the Patient Protection and Affordable Care Act to a single-payer national health insurance system that would cover every American. These policy debates lend particular salience to studies evaluating the health effects of insurance coverage. In 2002, an Institute of Medicine review concluded that lack of insurance increases mortality, but several relevant studies have appeared since that time. This article summarizes current evidence concerning the relationship of insurance and mortality. The evidence strengthens confidence in the Institute of Medicine's conclusion that health insurance saves lives: The odds of dying among the insured relative to the uninsured is 0.71 to 0.97.