This paper provides an empirical analysis of the effect of employer-provided health insurance and Medicare in determining retirement behavior. Using data from the Health and Retirement Study, we estimate the first dynamic  programming model of retirement that accounts for both saving and uncertain medical expenses. Our results suggest that uncertainty and saving are both important. We find that workers value health insurance well in excess of its actuarial cost, and that access to health insurance has a significant effect on retirement behavior, which is consistent with the empirical evidence. As a result, shifting the Medicare eligibility age to 67 would cause a significant retirement delay—as large as the delay from shifting the Social Security normal retirement age from 65 to 67.