Since their inception in the late 1980s, drug courts have become the most prevalent specialty court in the United States. A large body of outcome research conducted over the past two decades has demonstrated that drug courts effectively reduce drug use and criminal recidivism, which has led to the rapid proliferation of these courts. Importantly, drug court research has flourished despite the many challenges faced by researchers when working with a vulnerable population of justice-involved substance users. In this article, we highlight the most common methodological, ethical, and legal challenges encountered in drug court research, and discuss ways in which researchers can overcome these challenges to conduct high-quality research. Drug court research exemplifies how rigorous empirical investigation can be accomplished in the criminal justice system, and it can serve as a useful model for researchers working in other parts of the judicial system.