This study evaluates the Ohio Department of Alcohol and Drug Addiction Services' prison-based therapeutic communities (TCs) for inmates with histories of drug abuse. The study compares arrests/charges following release from prison among 487 inmates with TC experience and 242 inmates without TC treatment. Outcome measures were based on arrest and charge statistics. The results of survival analysis and Cox hazards model analysis indicate that length of time in the TC is crucial to a positive outcome. Controlling for age, gender, ethnicity, and education, inmates who spent at least 180 days in a TC were significantly less likely than those with less time in treatment or no TC exposure to be re-arrested/charged with violent or drug-related crimes one year after release.