The purpose of the present study was to determine whether drug self-administration by methadone maintenance clients can be influenced by offering methadone clinic privileges contingent upon reductions in drug use, and to compare the reinforcing efficacy in this regard of two different clinic privileges. Eight methadone maintenance clients who had histories of supplemental benzodiazepine use participated. In order to transfer illicit drug use to the treatment clinic, clients were prescribed diazepam, 20 mg/day, at the methadone clinic dispensary. Following assessment of baseline diazepam use, clients were offered, during 6-week blocks of time, either the chance to obtain a single methadone take-home dose or the chance to self-regulate their methadone dose for a single day. These privileges were contingent upon refusing prescribed diazepam at the clinic. During baseline weeks, 95.6% of available diazepam doses were requested. When take-home privileges were available, only 11.2% of diazepam doses were requested, while when dose self-control was available, 69.7% of doses were requested. The study showed that the supplemental drug use of methadone maintenance clients can be influenced by clinic privileges which are available contingent upon reductions of drug use. The medication take-home privilege was more effective as a reinforcer than was limited methadone dosage self-control. Methadone clinic privileges can be used as intervention tools to promote desirable therapeutic behavior change in drug addicts, and in particular to promote reductions in supplemental drug use.