Background Needle and syringe programmes (NSP) aim to reduce the risk of HIV by providing people who inject drugs (PWID) with sterile injecting equipment. A recent review of reviews (ROR) concluded that there was only tentative evidence to support the effectiveness of NSP in reducing HIV. We carried out a systematic review and meta-analysis to assess the association between NSP and HIV transmission. Methods Relevant primary articles presenting data on the risk of HIV transmission associated with NSP were identified in two stages: (i) from reviews identified in two published RORs (covering the period 1980-2008); and (ii) a literature search of CINAHL, Cochrane Library, EMBASE, MEDLINE and PsychINFO for primary articles published since the most recent high quality review (covering the period 2008-12). Study results were synthesized using randomeffects meta-analysis. Results There were 12 studies comprising at least 12 000 person-years of follow-up. Exposure to NSP was associated with a reduction in HIV transmission: pooled effect size 0 66 [95 confidence interval (CI) 0 43, 1 01] across all studies, and 0 42 (95 CI 0 22, 0 81) across six higher quality studies (according to the Newcastle-Ottawa tool). Conclusions There is evidence to support the effectiveness of NSP in reducing the transmission of HIV among PWID, although it is likely that other harm reduction interventions have also contributed to the observed reduction in HIV risk. NSP should be considered as just one component of a programme of interventions to reduce both injecting risk and other types of HIV risk behaviour.