Addiction may be perceived as a progressive disease, or as an adaptation of key neuroreceptors, depending on the viewpoint of the observer. Factors influencing changes in addictive behavior may have a psychological and/or pharmacological basis. Innovation, changes in personal ideology and intention, changes in personal relationships, and socio-economics and legal factors each play a role in the changing use of addictive substances. This book addresses the many processes of change affecting substance abuse from a multidisciplinary perspective. It results from a meeting organized by the Society for the Study of Addiction in 1992, with further invited contributions.