The aim of this study was to analyze information concerning multiple drug addiction, illicit behaviors and use of the venous route by maintenance treatment patients included in the October 1998 survey of the OPPIDUM program. Among 1,462 observations, 71% of the subjects were taking maintenance treatments (60% high-dose buprenorphine and 40% methadone). High-dose buprenorphine was taken without medical supervision in 10% of cases. Indicators of abuse were high in this case: multiple drug addiction and intravenous use of buprenorphine (28%). Patients maintained by methadone were older and living in better socio-economic conditions than patients maintained by high-dose buprenorphine. However, in the two groups, the percentage of patients using the intravenous route was the same (15% and 21%). More cocaine was used by the methadone group (16% versus 7%). Thirty-seven percent of the subjects maintained on high-dose buprenorphine were followed by a general practitioner. They appeared to be more unbalanced and in more precarious condition than subjects treated in specialized care centers but they were not representative of the patients maintained by buprenorphine. It would be important to determine why these subjects consult a specialized care center.