We investigate the impact on mortality of the world's rst compulsory health insurance, established by Otto von Bismarck, Chancellor of the German Empire, in 1884. Multiple empirical approaches, based on international comparisons and dierence-in-dierences strategies using Prussian administrative panel data to exploit dierences in eligibility for insurance across occupations, yield a consistent pattern suggesting that Bismarck's Health Insurance generated a signi cant mortality reduction. The results are largely driven by a decline of deaths from infectious diseases. We present prima facie evidence that diusion of new hygiene knowledge through physicians was an important channel. |