Abstract This paper examines the prevalence of benzodiazepine use, and its relationship to other drug use and HIV risk-taking among a sample of 1245 injecting drug users (IDU). Approximately a third (36.6%) of the sample had used benzodiazepines during their last typical month of injecting. Benzodiazepine users had injected more frequently, injected more heroin and amphetamines, and had more poly-drug use than other IDU. They also had higher levels of HIV risk-taking, having shared injecting equipment more frequently and with more people. There were no differences between groups in number of sexual partners or condom use, although benzodiazepine users were more likely to have been paid for sex. The demographic and drug use variables indicate that benzodiazepine users are a more dysfunctional subgroup of IDU who require particular attention in HIV interventions.