The focus of this article is criminal drug users and their changing behavior. Two important considerations are addressed within this topic. First, an overview of drug use is given, including a brief historical perspective on its treatment as well as its implications on crime. The article also discusses why substance abuse treatment in the criminal population is necessary and on what scale. Specifically, the etiology of the relationship between crime, violence and substance abuse is explored. It then delves into what has worked and what hasn't. Finally, recommendations are made regarding where the research indicates we should go from here.