Research on treatment outcome for addictive disorders indicates that a variety of interventions are effective. However, the progress clients make in treatment frequently is undermined by the lack of an alcohol and drug free living environment supporting sustained recovery. This book suggests that treatment providers have not paid sufficient attention to the social environments where clients live after residential treatment or while attending outpatient programs. It also describes the need for alcohol and drug free living environments.We then review the history of communal living for recovering addicts and alcoholics and provide concrete examples of the Oxford House model, which is a widespread communal living option for over 10, 000 recovering persons in the US. The structure and philosophy of Oxford Houses are presented along with recent outcome studies providing support for their effectiveness.This book was published as a special issue in the Journal of Groups in Addiction and Recovery.