Situational crime prevention has been the most important theoretical framework for understanding and designing effective crime reduction strategies. This chapter examines the contribution of the theory to success in applied settings. In addition, associated theories of rational choice, routine activity and problem oriented policing are examined. Implications for the security industry are considered, along with the problem of the 'security gap' in modern society. The chapter concludes by analysing a number of criticisms that have been made of situational prevention. Issues of displacement, inconvenience and inequality need to be taken into account when planning and evaluating crime prevention projects. However, these potential problems should not be seen as inevitable and should not inhibit project managers and security managers from making the most of situational prevention techniques.