The positive relationship between SES and health is well documented but limited evidence exists regarding the effect of an exogenous manipulation of SES on health. This article estimates the effect of promotions on heart disease using data on British civil servants from the Whitehall II study. Differences in promotion rates across departments and cohorts generate plausibly exogenous variation in promotion opportunities. The results suggest that promotions may reduce the probability of developing heart disease by 2.6–12.8 percentage points over a 15-year period. These estimates appear robust and are several times larger than cross-sectional estimates.