Guns themselves and their ready availability may be the problem, or the larger social issues behind violence may be the problem, but incomplete information no doubt gets in the way of dispassionate discussion and policy-making. Here, contributors describe the objective and scientific information that needs to be accumulated and analyzed before any real work can be done on the issue of gun-related violence, including data for measuring violence as it relates to gun ownership, patterns of firearm-related violence, illegal firearm acquisition, the use of firearms in defense against criminals, the use of firearms in suicide, right-to-carry laws, injury prevention programs, and judicial intervention.