Previous research has examined the effectiveness of drug treatment programs on reducing postrelease relapse and recidivism among offenders. However, little is known about how drug treatment programs for inmates affect their behavior within correctional institutions. What is known is that drug-involved inmates are among the most disruptive segment of the inmate population, causing increased violence and other rule violations within the institution. In order to determine if drug treatment programs for inmates reduce problematic behaviors among this group, the authors randomly assigned 170 prerelease inmates with histories of drug abuse to either weekly cognitive-behavioral counseling or brief monthly supportive counseling for a 6-month period. Outcomes under examination included reclassification to a greater security, self-reported commission of major rule violations, and citations received for rule violations. Results of multivariate statistical analyses revealed that the cognitive-behavioral treatment was correlated with a reduced likelihood of being reclassified to a high security level. However, the findings were mixed in that the cognitive-behavioral counseling did not have a significant effect on major rule violations or citations received for rule violations, which presumably influenced the decision to reclassify offenders to higher security environments. Limitations of the study include the fact that there was no comparison of the two treatment groups to a no-treatment control group. Tables, references