Prior to 2006, meta-analyses of the effectiveness of JDTCs concluded that they reduced delinquency by an average of only about 3-5 percent more than comparison programs; however, newer findings show increased effectiveness of JDTCs, which suggests that programs may be improving their operations over time. A recent large-scale study in Utah found that participants in four JDTCs (n = 622) reoffended at a significantly lower rate than a matched comparison sample of juvenile drug-involved probationers (n = 596). At 30 months post-entry, 34 percent of the JDTC participants had been rearrested for as new juvenile or adult offense compared to 48 percent of the probationers. Evaluators are just beginning to measure the cost-benefits and cost-effectiveness of JDTCs. A cost evaluation of a JDTC in Maryland reported net savings that exceeded $5,000 per participant over 2 years. The research shows that when JDTCs have committed to incorporating evidence-based treatments into their curricula and reached out to caregivers in the youths' social environments, reductions in delinquency and substance abuse have been as high as 15 to 40 percent. Poor results have typically been found for programs that have not developed evidence-based treatments, neglected to include family members or other caregivers in interventions, or failed to tailor interventions to the cognitive and maturational levels of the juveniles. Specific practices that are associated with successful JDTCs are requiring parents or guardians to attend status hearings; holding status hearings in court in front of a judge; avoiding reliance on costly detention sanctions; reducing youths' associations with drug-using and delinquent peers; enhancing parents' or guardians' supervision of their teens; and modeling effective disciplinary practices. 28 references