OBJECTIVES: Hand-hygiene amongst healthcare workers is amongst the most effective measures to reduce healthcare-associated infections, but compliance is often poor and little is known about the relative effectiveness of interventions to improve it. This study aimed to evaluate the effectiveness of hand-hygiene promotion interventions and to study the association between levels of investment in interventions and improved compliance. METHODS: A search strategy was developed and electronic databases searched for studies published before March 2014. Studies failing to meet the Cochrane Effective Practice and Organisation of Care Group (EPOC) inclusion criteria were rejected. Where studies had not used appropriate analytical methods, we re-analysed primary data. Information on resources required for interventions was extracted, and graded into three levels. Random effects meta-analysis was performed on studies considered sufficiently homogeneous with regard to interventions, participants and outcome measures.  RESULTS: Of 3,725 studies retrieved, 125 met inclusion criteria; 35 of these met EPOC criteria (6 randomised controlled trials (RCTs), 25 interrupted time-series (ITS), 2 controlled trials, and 2 controlled before-and-after studies). In four RCTs, hand-hygiene compliance was the primary outcome. Meta-analysis of these showed the intervention was associated with improved compliance (pooled odds ratio [OR], 1.39; 95%CI, 1.15-1.67, I= 80.00%). Of the 13 ITS studies, 12 showed significant stepwise increases in hand-hygiene compliance. All but three of these also showed a post-intervention trend for increasing hand-hygiene compliance.  Grouping studies by the level of investment, 22 were graded as resource-intensive while 11 and 2 studies had medium or low levels of investment, respectively. We found no evidence of a relationship between the level of investment and effect size. CONCLUSIONS: Hand hygiene promotion has a positive impact on hand hygiene compliance, but evidence that increased investment in hand hygiene leads to larger improvements is lacking. Reporting on resources used for interventions was, however, poor.