Harm reduction is an umbrella term for interventions aiming to reduce the problematic effects of behaviors. Although harm reduction was originally and most frequently associated with substance use, it is increasingly being applied to a multitude of other behavioral disorders. This article reviews the state of empirical research on harm reduction practices including alcohol interventions for youth, college students, and a variety of other adult interventions. We also review nicotine replacement and opioid substitution, as well as needle exchanges and safe injection sites for intravenous drug users. Dozens of peer‐reviewed controlled trial publications provide support for the effectiveness of harm reduction for a multitude of clients and disorders without indications of iatrogenic effects. Harm reduction interventions provide additional tools for clinicians working with clients who, for whatever reason, may not be ready, willing, or able to pursue full abstinence as a goal. © 2010 Wiley Periodicals, Inc. J Clin Psychol: In Session 66: 1–14, 2010.