Researchers have begun to look at the inner workings of drug courts and to investigate how key functional drug court components, singly and in combination, affect outcomes. When the evidence base resulting from such research is sufficiently strong to support meaningful conclusions about effectiveness, research can be translated into practice. This compendium presents findings from several recent studies that speak to the concerns of practitioners and policymakers about "what works." Sometimes the studies confirm what previous research has found, and sometimes they raise more questions than they answer. But in every instance, they contribute to the slowly building base of knowledge about "the drug court effect."