OBJECTIVES: In this study we explored the association between rates of household firearm ownership and homicide across the United States, by age groups. METHODS: We used cross-sectional time-series data (1988-1997) to estimate the association between rates of household firearm ownership and homicide. RESULTS: In region- and state-level analyses, a robust association between rates of household firearm ownership and homicide was found. Regionally, the association exists for victims aged 5 to 14 years and those 35 years and older. At the state level, the association exists for every age group over age 5, even after controlling for poverty, urbanization, unemployment, alcohol consumption, and nonlethal violent crime. CONCLUSIONS: Although our study cannot determine causation, we found that in areas where household firearm ownership rates were higher, a disproportionately large number of people died from homicide.