In 2009, the Bureau of Alcohol, Tobacco, Firearms and Explosives successfully traced over 145,000 guns recovered at crime scenes in the United States. Of these guns, more than 43,000 were originally sold in a different state from which they were recovered. What factors may explain the interstate movement of these crime guns? This article uses the well‐known gravity model of international trade to estimate interstate flow of crime guns. Empirical results show that, like trade of goods and services between nations, the traced movement of crime guns between states is proportionate to the economic sizes of trading partners and is inversely proportionate to the distance between them. In addition, the presence of gangs in one or both states tends to increase the flow of crime guns. Finally, differences in state gun laws tend to affect trade flows with crime guns flowing from states with “weak” gun laws to states with “strict” gun laws. (JEL K00, K42)