Phase I of MADCE entailed developing an evaluation protocol, a framework based on the program logic model, and a sample frame confirmed by a 2004 survey of practices completed by 380 drug courts. Phase II consisted of a mixed-method research project with qualitative and quasi-experimental designs implemented between 2005 and 2010, where data from 1,156 drug court and 625 non-drug court participants were sampled including interviews, drug tests, administrative records, court observation and interviews, and budget and other cost information. Results indicated that adult drug courts: 1) Significantly reduce drug use and criminal offending during and after participation, participants reported less drug use and were less likely to test positive on drug tests, and reported less criminal activity and had fewer re-arrests. 2) Are more cost efficient than current case processing/supervision practices, the net benefit of drug courts is an average of $5,680 to $6,208 per participant, depending on assumptions concerning participant income estimates. Most offenders who participated in drug courts had better outcomes than offenders who did not. However, the impact of drug courts was greater for participants with more serious prior drug use and criminal histories. The impact was smaller for participants who were younger, male, African-American, or who had mental health problems. Findings suggest that drug testing, legal leverage, and drug court judges are keys to program compliance and success; specifically, more status hearings, praise, and respectful interactions led to positive attitudes and outcomes. Compared to traditional case processing and supervision, drug courts have: higher investment costs related to greater substance abuse treatment access; lower police, court and corrections costs; and savings associated with fewer crimes, re-arrests, and incarceration. Drug courts that target offenders with high crime/high substance abuse risk yield the most effective interventions and maximize return on investment.