This paper proposes a research agenda that should explore (1) the effects of firearm use on the costs of violence; (2) the extent to which particular interventions can reduce the cost of violence by limiting use of firearms; and (3) the extent to which the benefits derived from firearm interventions are worth their public & private costs. Public health researchers can investigate many of the key issues in firearms & violence, but only if they expand their knowledge about guns & gun controls.