Background: Drug strategies internationally recognize link between drug use and crime. This review consider interventions for drug-using offenders under the care of the criminal justice system.; Objectives: To assess the effectiveness of interventions for drug-using offenders in reducing criminal activity and drug use in the courts, secure establishments and community-based settings.; Search Strategy: Twenty two electronic databases were searched (1980 to 2004). Internet sites and experts in the field were contacted for further information.; Selection Criteria: Randomised Controlled Trials designed to reduce, eliminate or prevent relapse in drug using offenders; Data Collection and Analysis: Two authors independently assessed trials for inclusion. Data were extracted by one author and double checked.; Main Results: Twenty four studies, 8936 participants, met the inclusion criteria. Results show that comparing a court-based community pre-trial release with drugs testing and sanctions versus routine pre-trial, for arrest at 90 days results favoured the comparison group OR 1.33 (95% CI 1.04 to 1.70). Comparing therapeutic community with aftercare with a mental health programme with a waiting list control, considering incarceration at 12 months OR 0.37 (95% CI 0.16 to 0.87), results in favour of the treatment Comparing intensive supervision with routine parole/probation, for recidivism OR 1.98 (95% CI 1.01 to 3.87) results in favour of comparison group, no statistically significant difference between the groups for arrest OR 1.49 (95% CI 0.88 to 2.51), drug arrest OR 1.10 (95% CI 0.50 to 2.39), conviction OR 0.93 (95% CI 0.55 to 1.58 ) and incarceration at one year OR 0.88 (95% CI 0.50, 1.54). Comparing intensive supervision and increased surveillance with intensive supervision alone, no statistically significant difference between the groups for recidivism OR 2.09 (95% CI, 0.86 to 5.07), arrest OR 1.22 (95% CI 0.51 to 2.88]), drug arrest, OR 1.29 (95% CI 0.35 to 4.85), conviction OR0.1.14 (95% CI, 0.22, to 5.91) and incarceration OR 1.30 (95% CI 0.39, to 4.30]) at one year.; Authors' Conclusions: Limited conclusions can be drawn about the effectiveness of drug treatment programmes for drug-using offenders in the courts or the community. This is partly due to the broad range of studies and the heterogenity of the different outcome measures presented. Therapeutic communities with aftercare show promising results for the reduction of drug use and criminal activity in drug using offenders. Standardisation of outcome measures and costing methodology would help improve the quality of research conducted in the area.;