Factors predicting the behavior change of drug-using detainees were investigated in detainees in two penitentiaries in The Netherlands. Subjects attended either a standard program or a Drug-Free Detention Program (DFDP) and were assessed at the beginning of detention, at release/transfer, and at 2 years after the end of detention. Predictors of postprogram contact with treatment agencies and changes in criminal recidivism, substance abuse, and psychosocial functioning were investigated using regression analysis. Detainees who started drug use early, without previous DFDP detention, and who frequently expressed self-esteem and who had many family problems realized meetings with drug treatment agencies more often. Those with a legal source of income showed decreases in addiction severity and in the number of days in which hard drugs were used. Comparison of the normal program and the DFDP showed that only for the normal wing could changes in substance use and psychosocial functioning be predicted. Results show the value of multiple-outcome criteria in criminal recidivism research and call for more studies investigating change processes.