Drug-induced alterations in gene expression throughout the reward circuitry of the brain are likely components of the persistence of the drug-addicted state. Recent studies examining the molecular mechanisms controlling drug-induced transcriptional, behavioral, and synaptic plasticity have indicated a direct role for chromatin remodeling in the regulation and stability of drug-mediated neuronal gene programs, and the subsequent promulgation of addictive behaviors. In this review, we discuss recent advances in our understanding of chromatin phenomena--or epigenetics, by one definition--that contribute to drug addiction, with the hope that such mechanistic insights may aid in the development of novel therapeutics for future treatments of addiction.