 Mass casualty shootings in public places have occurred regularly in the United States in recent years, prompting action from government. But deaths from mass shootings actually make up a very small percentage of firearm-related deaths in the U.S. So what does firearm violence in the U.S. actually look like? To inform public debate and to help guide legislation on the prevention of firearm-related deaths and injuries, it is instructive to consider the epidemiology of firearm violence over the past decade. The first thing to note is that compared with other nations, the United States is an outlier in mortality from firearm violence. Its rates of firearm homicide and suicide both substantially exceed those for the other industrialized nations in the Organization for Economic Cooperation and Development, the OECD. This finding is not likely due to a predisposition to violence in the United States, however, because among those same OECD nations, the U.S. ranks near the bottom in its prevalence of self-reported assault. The most recent data available reveal that between 2003 and 2012, more than 300,000 people died from firearm-related injuries in the United States. That's more than the number of U.S. combat-related deaths in World War II, and more than the total death count for all other U.S. wars combined. And while the overall fatality rate from firearm violence remained constant between 2003 and 2012, at almost 10 deaths per 100,000 persons per year, this stability masks a notable divergence. Firearm homicides have decreased since 2006, while suicides have risen by the same amount. Suicide has been the most common form of fatal gun violence over the past 30 years, and in 2012 accounted for 64% of fatal firearm violence. Gun homicide is concentrated to a remarkable degree among black males, especially young black men. In 2012, the gun homicide rate for black males aged 20 to 29 was almost 18 deaths per 100,000 persons, which is five times higher than that for Hispanic males, and 20 times higher than that for white males. The pattern for firearm homicide among females is similar to that for males, but the rates are lower by a factor of 10. Black females aged 20 to 24 had the highest mortality rate in 2012, with approximately 7.5 deaths per 100,000 persons. The risk of gun suicide, on the other hand, is highest among white males. In 2012, suicide rates for white males peaked at 40 deaths per 100,000 persons among 80 to 84 year olds, while the rate for Hispanic men was below 15, and that for black men was below 10 per 100,000 persons. Between 1999 and 2012, the death rate due to firearms increased along white males aged 35 to 64 by almost 36%. White females are similarly more prone to firearms suicide than black or Hispanic females, although the number of cases is lower than male cases by a factor of 10. It peaks at 4.5 per 100,000 persons among white women aged 45 to 55. The societal costs of firearm suicides and homicides are enormous. For 2010, the estimated cost was $164.6 billion, approximately 1.1% of the US gross domestic product for that year. While there are many factors associated with the risk of death from firearm violence, the most widespread appears to be gun ownership. The US is home to more than 50 million firearm owners, approximately 35% of men and 11% of women report owning firearms. Further research on the nature and prevention of firearm violence is sorely needed. Evidence-based interventions may lead to substantial reductions in death and disability from this important public health problem.