The purpose of this paper is to describe what harm reduction is, how it developed, how it works, and why it is becoming a major approach in the addictive behaviors field. Based on principles of public health, harm reduction offers a pragmatic yet compassionate set of strategies designed to reduce the harmful consequences of addictive behavior for both drug consumers and the communities in which they liver. To illustrate how harm reduction has been applied to both the prevention and treatment of addiction problems, highlights of a national conference on harm reduction are presented. The historical roots of harm reduction programs in Europe (Netherlands and the United Kingdom) are described. The paper concludes with a discussion of four basic assumptions central to harm reduction: (a) harm reduction is a public health alternative to the moral/criminal and disease models of drug use and addiction; (b) it recognizes abstinence as an ideal outcome but accepts alternatives that reduce harm; (c) it has emerged primarily as a "bottom-up" approach based on addict advocacy, rather than a "top-down" policy established by addiction professionals; and (d) it promotes low threshold access to services as an alternative to traditional high threshold approaches.