We study the impact of social health insurance on mortality. Using the introduction of compulsory health insurance in the German Empire in 1884 as a natural experiment, we estimate difference-in-differences and regional fixed effects models exploiting variation in eligibility for insurance across occupations. Our findings suggest that Bismarck’s health insurance generated a significant mortality reduction. Despite the absence of antibiotics and most vaccines, we find the results to be largely driven by a decline of deaths from infectious diseases. Further evidence suggests that statutory access to well-trained doctors was an elementary channel. This finding may be explained by insurance fund physicians transmitting new knowledge on infectious disease prevention.