A retrospective study was carried out using 3 606 medical files of nine detention centers in France, over a three-month period (May to July 1997). The files were analyzed to determine, age, type of addiction and subsequent type of therapy proposed: methadone, high-dose buprenorphine or abstinence. A comparison was then made to determine whether or not there exists a statistical relationship between the type of therapy given in prison for drug abuse and subsequent recurrent use during the following three and a half years, until December 2000.