BACKGROUND: A systematic review was conducted to determine whether behavioural interventions are effective in preventing transmission of hepatitis C virus (HCV) amongst people who inject drugs. METHODS: Medline, EMBASE, the Cochrane Clinical Trial Database, PSYCHINFO and hand-searching of bibliographies were used to identify controlled trials of behavioural interventions for reducing HCV transmission amongst people who inject drugs. Behavioural interventions were defined as non-pharmacological interventions that aimed to change individual behaviours without explicitly attempting to change population norms. RESULTS: Six trials evaluating peer-education training and counselling interventions were included in the review. There was considerable variation between trials with respect to intervention duration, control and study population. Trials evaluated the impact of interventions on HCV incidence (three studies, 1041 participants) and frequency of injecting risk behaviours (six studies, 2472 participants). Amongst the three studies which measured the impact of the intervention on HCV incidence, none found a statistically significant difference between intervention and control groups. Measures of frequency of injecting risk behaviours varied greatly and could not be pooled. Only two studies (n=418, 854) showed significantly greater reductions in injecting risk behaviours in the intervention group compared with the control group. CONCLUSIONS: There was considerable variation in study design, outcome measures and magnitude, direction and statistical significance of findings between studies. Nonetheless, it is unlikely that behavioural interventions can have a considerable effect on HCV transmission. It is likely that multi-component interventions are required.