With growing numbers of drug-involved offenders, substance abuse treatment has become a critical part of corrections. A multistage therapeutic community implemented in the Delaware correctional system has as its centerpiece a residential treatment program during work release--the transition between prison and community. An evaluation of this program followed 690 individuals. At 5 years, those who participated in the program were significantly more likely to be drug and arrest free. Furthermore, treatment graduates with or without aftercare had significantly greater probabilities of remaining both arrest free and drug free than did a "no treatment" comparison group in regular work release. Dropouts also were significantly more likely to be drug free, although not significantly less likely to have a new arrest than those without treatment. These data show that the implementation of such programs could bring about significant reductions in both drug use and drug-related crime. (Contains 5 tables and 1 figure.)