Presents an evaluation and outcome study of the Ozarks Correctional Center Drug Treatment Program (OCCDTP), a prison based substance abuse therapeutic community. Therapeutic communities (TCs) recognize that inmates who are paroled or released often must return to the environments in which they first turned to crime. TCs are structured so that individuals will develop their own ability to solve problems in such an environment. Outcome studies consistently have indicated that inmates who successfully complete the phases of a TC drug treatment program are less likely to be arrested or report using drugs after discharge than similar inmates who do not participate. This evaluation compares 161 male program graduates (mean age 35 yrs) to a control group of inmates in Missouri who had similar substance abuse problems but did not attend the program. Results from this short term evaluation of OCCDTP supports the utility of TCs in changing attitudes, creating healthier prison environments, and ultimately reducing recidivism. Attention to longer term outcomes, to aftercare variation, to program dropouts, and to subpopulation differences in patterns of recovery define evaluation work yet to be completed. (PsycINFO Database Record (c) 2019 APA, all rights reserved)