The 1918 influenza epidemic had a marked and fairly long‐lasting effect on the sex differential in mortality in the United States. After 1918 women lost most of their mortality advantage over men and the female/male gap did not regain its pre‐epidemic level until the 1930s. An analysis of causes of deaths shows a link with tuberculosis. We conjecture the existence of a selection effect, whereby many 1918 influenza deaths were among tuberculous persons, so that tuberculosis death rates dropped in later years, disproportionately among males. Age‐ and sex‐specific data by cause of death corroborate this hypothesis.