Recent advances in the fields of genetics, molecular biology, behavioral neuropharmacology, and brain imaging have dramatically changed our understanding of the addictive process and why relapse occurs even in the face of catastrophic consequences. Addiction is now recognized as a chronic brain disease that involves complex interactions between repeated exposure to drugs, biological (i.e., genetic and developmental), and environmental (i.e., drug availability, social, and economic variables) factors. Its treatment, therefore, requires, in general, not only a long-term intervention but also a multipronged approach that addresses the psychiatric, medical, legal, and social consequences of addiction. Also, because addiction usually starts in adolescence or early adulthood and is frequently comorbid with mental illness, we need to expand our treatment interventions in this age group both for substance abuse and psychiatric disorders.