Rationale: Asthma is a multi-factorial disease; genetic factors have been suggested but have not been well defined. Objectives: This study examined evidence for a heritable component to asthma mortality using a unique data resource consisting of Utah death certificates linked to a genealogy of Utah. Methods: Cases were defined as individuals whose death certificate listed asthma as a cause of death in a registry of all Utah deaths since 1904 (n=1,553). The genealogical index of familiality analysis was used to compare the average relatedness of asthma deaths to the expected relatedness in the Utah population. Relative risks for asthma death in relatives of individuals who died from asthma are provided for close and distant relatives. Measurements and Main Results: The genealogical index of familiality identified a significantly higher average relatedness in cases (p<0.001), even when close relationships were ignored. In addition, a significantly increased risk of dying from asthma was observed in first-degree relatives of cases (relative risk = 1.69, p<0.001) and in second-degree relatives of cases (relative risk = 1.34, p=0.003). Conclusions: These results support a heritable contribution to asthma mortality.