Chapter 3 has described in some depth the nature of urban crime and violence as they are experienced across the world. The purpose of this chapter is to examine some of the policy responses to these problems, and to explore some of the available evidence on how successful these initiatives have been. It needs to be understood, from the outset, that a high proportion of these initiatives have not been fully or properly evaluated, and that a further proportion have either not had the results of such evaluations made public at all or have done this in ways that are not readily accessible. It is also the case that much of the evidence that is available and accessible comes from the developed world, rather than from the developing world, and it should not be automatically assumed that conclusions from the former context will automatically apply to the latter. Consequently, the evidence based on what works is much thinner than the plethora of initiatives to be found.