The findings indicate that participants in drug courts have lower recidivism than non-participants; however, the magnitude of this effect varies by type of drug court. For adult drug courts, the average effect of participation is a reduction in general recidivism from 50 percent to approximately 38 percent and a reduction in drug-related offenses from 50 percent to approximately 37 percent. These recidivism declines persisted for at least 3 years after entering the program. These findings warrant continued funding, operation, and expansion of adult drug courts. For DWI (driving while intoxicated) courts, the reduction in recidivism after program entry are comparable to the effect of adult drug courts; however, given the mixed findings for DWI drug courts that have been subjected to the most rigorous, randomized experimental evaluations, additional experimental evaluations of DWI courts are warranted before firm conclusions about their effects can be made. Juvenile drug courts - in contrast to the moderate recidivism-reduction effects of adult and DWI drug courts - have had relatively small effects on the recidivism of participants. For juvenile drug courts, the reduction in recidivism is just over 40 percent smaller than the average estimated effect of participation in an adult or DWI drug court. The authors offer two explanations for this difference: juvenile drug courts generally provide services to relatively high-risk offenders compared to the other types of drug courts; and juvenile drug courts apparently demand less from participants. The literature search identified 154 independent evaluations: 92 evaluations of adult drug courts, 34 evaluations of juvenile drug courts, and 28 evaluations of DWI drug courts. Meta-analysis was used to synthesize the findings. 6 tables, 3 figures, 11 notes, and 41 references