Drug courts have been in existence since 1989, yet few process evaluations have appeared in the literature to help inform the discussion about their effectiveness. This article reports findings from a process evaluation of a drug court program in San Mateo, California. The evaluation was designed to document the history of the program, to examine program strengths and areas of improvement, to access the roles and relationships among the various agencies involved and to describe the impact of the drug court program on the justice and drug treatment systems. Methods included review of available drug court program documents, interviews with key stakeholders, and focus groups with drug court participants. The main findings were: support for the continuation of drug court, enhanced collaboration among all agencies, and an increased awareness of the needs of substance-using clients in the criminal justice system. Potential lessons for other drug courts include the importance of building strong collaborations and maintaining good communication, recognizing competing interests in developing procedures for drug court, and considering changes in eligibility criteria as experience with drug court model expands.