Results included reduced recidivism for drug court participants up to 14 years after drug court entry compared to eligible offenders that did not participate. Drug court judges that worked longer with the drug court had better participant outcomes. Judges that rotated through the drug court twice had better participant outcomes the second time than the first. Compared to traditional criminal justice system processing, treatment and other investment costs averaged $1,392 lower per drug court participant. Reduced recidivism and other long-term program outcomes resulted in public savings of $6,744 on average ($12,218 if victimization costs are included), or an estimated $79 million over 10 years. The analysis of the data focused on the overall impact of the drug court on the target population over time, variations over time on that impact, and external and internal conditions that influenced these outcomes. A cost analysis was conducted to assess the overall investment of taxpayer money in the court compared to its benefits. This study covers the period from program start in 1991 through 2001. The entire population of offenders, identified as eligible for drug court by the Multnomah County District Attorney’s Office from 1991 to 2001, was identified and tracked through a variety of administrative data systems. Approximately 11,000 cases were identified; 6,500 participated in the Drug Court program during that period and 4,600 had their case processed outside the drug court model. Data on outcomes were gathered on each offender, with a particular emphasis on criminal recidivism. The outcome data were drawn in late 2005 and early 2006, allowing a minimum of 5 years of followup on all cohorts and more than 10 years on many cohorts. Data on costs were calculated in terms of investment costs, outcome costs, and total costs per participant.