BACKGROUND: Although guidelines recommend that people who inject drugs (PWID) should not be excluded from hepatitis C (HCV) treatment, some services remain reluctant to treat PWID. The aim of this review was to investigate sustained virologic response (SVR), adherence, discontinuation, and HCV reinfection among PWID. METHODS: A search of Medline, Embase, and Cochrane databases (between 2002 and January 2012) was conducted for primary articles/conference abstracts examining HCV treatment outcomes in PWID. Meta-analysis was used to obtain pooled estimates of SVR, adherence, discontinuation, and HCV reinfection. RESULTS: Ten primary articles and 1 conference abstract met the inclusion criteria. Across 6 studies (comprising 314 drug users, of whom 141 [45%] were PWID), pooled SVR was 56% (95% confidence interval [CI], 50%-61%) for all genotypes, 37% (95% CI, 26%-48%) for genotypes 1/4, and 67% (95% CI, 56%-78%) for genotypes 2/3. Pooled 80/80/80 adherence was 82% (95% CI, 74%-89%) across 2 studies, and pooled treatment discontinuation was 22% (95% CI, 16%-27%) across 4 studies. Across 5 studies (comprising 131 drug users) examining reinfection, pooled risk was 2.4 (95% CI, .9-6.1) per 100 person-years. CONCLUSIONS: HCV treatment outcomes are acceptable in PWID, supporting treatment guidelines. The pooled estimate of HCV reinfection risk was low, but there was considerable uncertainty around this estimate. Further studies on the risk of reinfection are needed to assess the long-term effectiveness of HCV treatment in PWID.