In the past almost 40 years, homicide rates in the United States have moved in cycles. The gender and race of victims and offenders have not changed significantly over time with males committing approximately 90 percent of all homicides and representing 75 percent of the victims. According to a Federal report, the homicide rate is higher in urban areas than in rural areas. Over 60 percent of all homicides in the United States in 1999 involved a firearm and firearm ownership in the United States, particularly handgun ownership, is much more common than in other developed nations. This article provides a review of the most commonly cited, representative, and empirical studies in the peer-reviewed literature that directly investigate the association between gun availability and homicide. The article begins by describing individual case control and cohort studies. Then, it describes international ecological studies that have compared the United States to other countries. Lastly, it describes ecological studies of the United States that have contrasted the levels of gun availability and homicide across regions, States, and rural and urban areas. The available evidence is quite consistent. The few case control studies suggest that households with firearms are at higher risk for homicide, particularly firearm homicide. International cross-sectional studies of high-income countries find that in countries with more firearms, both men and women are at higher risk for homicide, particularly firearm homicide. The strongest evidence came from cross-sectional analyses of United States regions and States. In summation, places with higher levels of gun ownership are places with higher homicide rates. Most studies, cross sectional or time series, international or domestic, are consistent with the hypothesis that higher levels of gun prevalence substantially increase the homicide rate. References