There is increasing evidence that the environment modifies individual genotypes through epigenetic mechanisms, creating behavioral traits and leaving persistent memories of past events. In post-mitotic cells such as neurons, chromatin modifications provide not only transient but also stable (or even permanent) epigenetic marks. These could promote, maintain or block transcriptional processes that, in turn, participate in the molecular adaptations underlying behavioral changes. Accordingly, epigenetics has become a central topic in several domains of neuroscience, including neurobiological approaches to drug addiction. In this chapter we summarize current evidence for the involvement of epigenetic mechanisms in the promotion of drug consumption and addictive behavior. We also suggest how the same epigenetic mechanisms could be used to improve the clinical management of these disorders.