A survey of a methadone treated population of 562 heroin addicts was undertaken to determine which factors linked to certain characteristics of the individual or to the cures, might be associated with either a positive outcome or failure. Furthermore it enabled the recording of various modifications with regard to social and professional integration, as well as tracing the penal career, both during the cure and to the cut-off date (31 July 1986). This paper presents the preliminary results of the survey in relation, firstly, to certain aspects of the individual's career in drug abuse, within a specific population; secondly, the various efforts towards detoxification and lastly the situation with regard to their state of drug addiction at the cut-off date.