Case management has been implemented in substance abuse treatment to improve (cost-) effectiveness, but controversy exists about its potential to realize this objective. A systematic and comprehensive review of peer-reviewed articles (n = 48) published between 1993 and 2003 is presented, focusing on the effects of different models of case management among various substance-abusing populations. Results show that several studies have reported positive effects, but only some randomized and controlled trials have demonstrated the effectiveness of case management compared with other interventions. Longitudinal effects of this intervention remain unclear. Although no compelling evidence was found for the effectiveness of case management, some evidence is available about the (differential) effectiveness of intensive case management and assertive community treatment for homeless and dually-diagnosed substance abusers. Strengths-based and generalist case management have proven to be relatively effective for substance abusers in general. Most positive effects concern reduced use of inpatient services and increased utilization of community-based services, prolonged treatment retention, improved quality of life, and high client satisfaction. Outcomes concerning drug use and psychosocial functioning are less consistent, but seem to be mediated by retention in treatment and case management. Further research is required to learn more about the extent of the effects of this intervention, how long these are sustained and what specific elements cause particular outcomes.