A follow-up study was done in 31 rehabilitation probands who were discharged consecutively from a long term drug withdrawal centre for heroin and multiple drug addiction. Referral had been on the basis of section 64 of the penal code and a motivation for treatment had to be established first. After discharge the majority of probands could be reassessed repeatedly. A total of 180 follow-up investigations included also urinanalysis and in 170 of these cannabinoids were looked for. Cannabis was detected in only two cases. When other addictives were demonstrated in a few cases they could be attributed to codeine-containing medicines beyond doubt. Regular follow-up assessments of past drug addicts including urinanalyses serve for further stabilisation of the patients and at the same time indicate long-term success of treatment.