This study examined outcomes for two treatment-based drug court programs during a 30-month follow-up period. Outcomes for drug court graduates were contrasted with those of nongraduates and of comparison groups that consisted of offenders who were placed on probation supervision during the same period and did not receive drug court services. Drug court graduates from both programs were significantly less likely to be arrested and had fewer arrests during follow-up in comparison to matched probationers and nongraduates. For both drug courts, the rates of arrest during the 30-month follow-up period declined in direct relationship to the duration of drug court involvement. Drug court graduates had lower rates of substance abuse than comparable groups of treated offenders. The implications for clinical practice and the need for additional drug court outcome research are discussed.