OBJECTIVES: To review the literature on the potential efficiency gains of integrating HIV services with other health services. DESIGN: Systematic literature review. Search of electronic databases, manual searching and snowball sampling. Studies that presented results on cost, efficiency or cost-effectiveness of integrated HIV services were included, focusing on low- and middle-income countries. Evidence was analysed and synthesised through a narrative approach and the quality of studies assessed. RESULTS: Of 666 citations retrieved, 46 were included (35 peer reviewed and 11 from grey literature). A range of integrated HIV services were found to be cost-effective compared with 'do-nothing' alternatives, including HIV services integrated into sexual and reproductive health services, integrated tuberculosis/HIV services and HIV services integrated into primary healthcare. The cost of integrated HIV counselling and testing is likely to be lower than that of stand-alone counselling and testing provision; however, evidence is limited on the comparative costs of other services, particularly HIV care and treatment. There is also little known about the most efficient model of integration, the efficiency gain from integration beyond the service level and any economic benefit to HIV service users. CONCLUSIONS: In the context of increasing political commitment and previous reviews suggesting a strong public health argument for the integration of HIV services, the authors found the evidence on efficiency broadly supports further efforts to integrate HIV services. However, key evidence gaps remain, and there is an urgent need for further research in this area.