Methadone maintenance patients who use benzodiazepine drugs were interviewed about the dosage levels, patterns, frequency and motives for their use of these drugs. The sample was drawn from two treatment clinics, one in Baltimore (N = 12) and one in Philadelphia (N = 17). Benzodiazepine use was prevalent at both of these clinics - 65-70% of maintenance patients had positive urinalysis tests during a single month. Ninety-three per cent of survey participants identified diazepam as the drug which they used most often. The median value of the usual daily dose was 40-45 mg, 31% reported usual daily doses between 70 and 300 mg and 62% had experience with doses of 100 mg and higher. The majority of the sample reported taking diazepam in a single daily dose within one hour of the time that they ingested their daily methadone; 72% of the sample indicated that diazepam boosts the effects obtained from the daily methadone dose. Another sample of addicts who reported extensive experience with both benzodiazepines and barbiturates indicated that diazepam increases the effects of methadone while barbiturates produce no change in the effects of methadone. Results of this study suggest that patterns and dosages of diazepam use among methadone maintenance patients are primarily abusive rather than therapeutic.