This article examines the role of drugs in increasing the incarcerated population in the United States. Research is increasingly demonstrating the effectiveness of treatment for incarcerated populations in reducing recidivism and drug use, especially treatment in a therapeutic community (TC). Transitional services that include TC treatment in a work release setting greatly reduce recidivism and relapse, as do aftercare services. Although treatment options are increasing in prisons, there are many more who could benefit from treatment than receive it. Much remains unknown about how to best reach drug-involved offenders to stop the revolving door of drug addiction and incarceration. This article touches on many relevant areas ripe for further research