A great deal of interest and research has been dedicated toward pharmacogenomics-that is, the study of genetic variation as it pertains to the use of drugs. Most commonly, the term is used to refer to heritable variability in the processes of pharmacokinetics (PK)—what the body does to the drug-and pharmacodynamics (PD)—what the drug does to the body. However, particularly in the context of drugs of abuse (DOA), the ’eld can be expanded to include concepts that go beyond pharmacology into the realms of psychology and neurology (1). Pharmacogenetic studies have addressed the importance of genetic variation in areas such as individual susceptibility to addiction, preference for a given DOA, or ability to cease drug use.