The term psychogenomics is used here to describe the process of applying the powerful tools of genomics and proteomics to achieve a better understanding of the biological substrates of normal behavior and of diseases of the brain that manifest themselves as behavioral abnormalities. Applying psychogenomics to the study of drug addiction will lead to the identification of genes and their protein products that control the reward pathways of the brain and their adaptations to drugs of abuse, as well as variations in these genes that confer genetic risk for addiction and related disorders. The ultimate goal is to use this information to develop more effective treatments for these disorders as well as objective diagnostic tools, preventive measures, and eventually cures.