To evaluate the extent to which the introduction (February 1996) of ambulatory prescriptions of buprenorphine for drug maintenance treatment (DMT) has been associated with its intravenous illicit use by French injecting drug users (IDUs). Cross-sectional survey (September 1997), using self-administered questionnaires, in a sample of IDUs recruited at 32 pharmacies, four needle exchange programmes and three syringe vending machines. Thirty-nine sites where IDUs have access to sterile syringes in the city of Marseille (South-Eastern France). Sample of IDUs attending community pharmacies, vending machines and needle exchange programs to obtain equipment. To compare characteristics of IDUs who declared that they only injected buprenorphine in the prior 6 months versus the rest of the sample. Among the 343 respondents (response rate = 70.7%), 33.8% were polydrug users who occasionally injected buprenorphine in parallel to heroin and/or cocaine, while 23.9% only injected buprenorphine in the previous 6 months. IDUs in this latter group were younger, injected more frequently, and were more frequently on buprenorphine DMT, but they were less likely to be HIV-infected and to declare HIV-related injecting risky behaviours. Substantial risk of injecting misuse is associated with large-scale diffusion of buprenorphine DMT. A more stringent regulation for medical dispensation of buprenorphine than the current French general freedom of prescription for all physicians, including general practiioners in ambulatory care, may be necessary in other countries which are considering the diffusion of buprenorphine DMT.