This paper presents the results of the first ever systematic review of street-level drug law enforcement interventions. The paper has undergone extensive review - both through the peer review process of the Journal of Experimental Criminology (where it is now published) as well as through the formal review processes of the Campbell Collaboration. An abdriged version of our research findings appear as the first in a new series published by the US Department of Justice's Office of Community Oriented Policing Services entitled Crime Prevention Research Reviews. The Journal of Experimental Criminology is recognised as a Tier 2 international journal by the University of Maryland criminology rankings process. A slighly modified version of the paper appears as one of ten sanctioned reviews of the Crime and Justice Group of the Campbell Collaboration (see http://www.campbellcollaboration.org/CCJG/index.asp). The Campbell Collaboration (C2) is an independent, international, non-profit organization that strives to provide decision-makers with evidence-based information to empower them to make well-informed decisions about the effects of interventions in the social, behavioral and educational arenas. The Campbell Collaboration is a partner with the internationally acclaimed Cochrane Collaboration and is supported by the American Institutes for Research (AIR), as well as a number of other international organizations, including the Norwegian and Danish governments.