BACKGROUND Unintentional injuries are one of the leading causes of death in the United States. Many of these injuries are preventable, and unintentional firearm injuries, in particular, may be responsive to prevention efforts. We investigated the relationship between unintentional firearm death and urbanicity among adults. METHODS This study was a retrospective analysis of national death certificate data. Unintentional adult firearm deaths in the United States from 1999 to 2006 were identified using the Multiple Cause of Death Data files from the National Center for Health Statistics. Decedents were assigned to a county of death and classified along an urban-rural continuum defined by population density and proximity to metropolitan areas. Total unintentional firearm death rates by county were analyzed in adjusted analyses using negative binomial regression. RESULTS A total of 4,595 unintentional firearm injury deaths of adults occurred in the United States during the study period (a mean of 574.4 per year). Adjusted rates of unintentional firearm death showed increases from urban to rural counties. Americans in the most rural counties were significantly more likely to die of unintentional firearm deaths than those in the most urban counties (relative rate, 2.16; 95% confidence interval, 1.44-3.21, p = 0.002). CONCLUSION Rates of unintentional firearm death are significantly higher in rural counties than in urban counties. Prevention strategies should be tailored to account for both geographic location and manner of firearm injury. LEVEL OF EVIDENCE Epidemiologic study, level III.