In most countries in the European Union, including Belgium, the approach of the drug problem is an integral and integrated one, in which several policy levels and policy domains are involved in the drug policy (EMCDDA, 2008). This approach requires a vertical policy concurring between the different competency levels (e.g. national and local level) and a horizontal policy concurring between the different policy domains (e.g. prevention, harm reduction, treatment, health and well-being and repression). Since the 1990’s, evaluation of policy has become increasingly important in western societies (Leeuw, 2005). In accordance with this tendency, evaluation has been executed in several domains involved in approaching the drug phenomenon. In scientific literature, studies are found evaluating interventions in the prevention (Stevens, Trace & Bewley-Taylor, 2005; Stevenson & Mitchell, 2003; Botvin & Griffin, 2003; Kumpfer & Alder, 2003), the treatment (Autrique, Vanderplasschen, Pham, Broekaert, & Sabbe, 2007; Rigter, van Gageldonk, Ketelaars, & van Laar, 2004; van Gageldonk, Ketelaars, & van Laar, 2006) and the law enforcement domain (Stevens et al., 2005; Mazerolle, Soole, & Rombouts, 2007). Studies evaluating the cooperation between several domains involved in approaching the drug phenomenon are rare though. When developing an evidence based drug policy, more insight in best practices in an integral and integrated drug policy are absolutely necessary. With this contribution, we try to answer the following research questions: first, in developing an integral and integrated drug policy, which international best practices can be identified (i.e. what works)? Second, how must we implement these interventions (i.e. how does it work)? Third, to what extent have these effective interventions and best practices been implemented in the Flemish Community? The aim of this chapter is to identify international best practices in developing an integral and integrated drug policy. No (new) evaluations of cross-cutting interventions were conducted, but by means of a study of literature, we present best practices in the context of developing an integral and integrated drug policy and the essential preconditions involved. These cross-cutting interventions and essential preconditions are better illustrated with reference to specific examples. To this end, we analyse to what extent these best practices have indeed been implemented in the Flemish Community. We will give two examples of best practices and two examples of less favourable practices in this Community of Belgium. In the first part of this contribution, we define the scope of this paper: we describe what is meant with an integral and integrated drug policy and we identify the actors involved. After a presentation of the methods used, we present the international best practices in an integral and integrated drug policy. Finally, we analyze how these international best practices are implemented in the Flemish Community. This chapter is based upon the research project “Do’s and don’ts in an integral and integrated drug policy” (De Ruyver, Lemaître, Ponsaers, Born, Pauwels, Vander Laenen et al., 2009). This research project started in October 2007 and ended in April 2009. The research project is part of the Research programme in support of the federal drug policy document and is funded by the Federal Science Policy.