Why are some people more likely than others to become addicted to drugs? What are the best ways to prevent and treat addiction? How should we shape our public policies about drug addiction? Scientific perspectives on drug abuse are changing, and this text provides a comprehensive introduction to current ideas and research about the causes of drug abuse and its prevention and treatment. It also crystallizes the effects that research and public attitudes can and do have on our national drug abuse policies. The theoretical perspectives presented here should be of interest to clinicians and scientists alike, as well as anyone who cares about the societal effects of drug abuse.