In recent years, few subjects in the field of addiction research have generated as much debate as the role of inpatient treatment for patients with substance use disorders (SUDs). This controversy has been fueled in part by the enormous cost of SUD treatment in the United States: in 2005, the direct cost for their treatment was estimated at $18 billion (Mark et al. 2005). In contrast, the annual cost to society of alcohol- and drug-related problems has been estimated to be more than $410 billion (Mojtabai and Zivin 2003). Therefore, establishing effective treatment methods for patients with SUDs is both a public health and a financial priority. Because the resources available to tackle this issue are finite, treatment should be not only effective but also cost-effective. While the treatment of SUDs overall has a favorable cost-benefit ratio compared with other medical care, questions have been raised about the cost-effectiveness of inpatient treatment for substance-related problems (Mojtabai and Zivin 2003). Because the cost differential between inpatient and outpatient treatment is substantial, and because there is wide variation in per diem costs even among inpatient facilities, determining the proper role of hospital treatment is critical.