Interventions for drug-using offenders are employed internationally to reduce subsequent drug use and criminal behavior. This paper provides information from a systematic review of 24 randomized controlled trials (RCTs) conducted between 1980 and 2004. Thirteen of the 24 trials were included in a series of meta-analyses, and tentative conclusions are drawn on the basis of the evidence. Pretrial release with drugs testing and intensive supervision were shown to have limited success when compared to routine parole and probation, with effect sizes favoring routine parole and probation. Therapeutic community interventions showed promising results when compared to dispensation of treatment to individuals as usual, reducing risk of future offending behavior. A few studies evaluated the effectiveness of assertive case management and other community-based programs, but due to the paucity of information few inferences could be drawn from these studies. Little is known about the cost and cost effectiveness of such interventions, and the development of established protocols is required.