This multidisciplinary encyclopedia first appeared as the Encyclopedia of Drugs and Alcohol (Macmillan Reference, 1995). The goal was to provide non-specialists with summaries of latest medical research on the effects of drugs and alcohol, the nature of addiction and approaches to treatment. The scientific studies were placed in a socio-political context with articles on the history of drug use, trafficking, law enforcement and social policy. Thus the range of topics included groups of drugs, physiological interactions, risk factors, and biological complications as well as types of abuse, legal issues and government policies. Although chemical dependency remained the primary focus, the second edition expanded the scope to include selected addictive behaviors such as eating disorders and gambling. Taking advantage of advances in genetics, brain imaging and epidemiology, this latest edition explores research on the underlying causes of addiction. Greater emphasis also is placed on support groups and behavioral approaches to treatment. While many entries still present social policies and drug enforcement in the United States, cross-cultural comparisons are possible with the addition of entries on drug abuse in numerous countries around the world. Other new entries examine the influence of the internet on drug use and the portrayal of drugs in the media. All told, 545 entries, alphabetically arranged from “abstinence violation effect” to zero tolerance, explore the use of drugs and alcohol in historic and contemporary contexts. more than two thirds cover new topics or have been substantially revised. Almost every bibliography has also been updated. The result is a substantial revision of a useful tool providing undergraduates and general readers with a wealth of information on a key issue in our society.