As with other pharmacogenomics studies, two potential targets for research on pharmacogenomics of medication treatment for drug addiction include genes encoding enzymes that metabolize the medications used in the treatment of addictions and genes encoding the putative neurochemical target of the pharmacotherapy. Examples of these two areas of research include genes encoding cytochrome P450 enzymes and genes encoding opiate receptors in studies of opiate agonists and antagonists for addiction. In addition to these two potential targets, drug addiction has a third potential area of research; drugs of abuse have known biochemical effects on the brain which could be altered by genetic variation in neurotransmitter receptors. Although these three areas could provide important lines of research in the development of medication for addiction, to date research in this area has not lived up to its potential, with the few studies that have been done on pharmacogenomics of medication treatment of addictions ’nding some inconsistent results. Recently genome-wide association studies (GWAS) have been done on the treatment response for medications for nicotine addiction with more consistent ’ndings across studies. This chapter will review the research done to date on pharmacogenomics of addiction medication and discuss potential future areas of research based on promising ’ndings in addiction treatment.