Drugs of abuse have effects at multiple biological and environmental levels. The environmental level is identified as “social,” since this is the most relevant of the environmental factors that influence drug abuse in humans. Imaging techniques allow one to assess the effects of drugs of abuse at the protein and the brain circuit levels and to assess how these effects relate to behavior. Imaging also offers a way to start to assess the impact of environmental factors on these biological levels, as well as the impact of gene polymorphisms on protein expression and brain function.