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The scaling up of HIV/AIDS programming has been one of the most extensive undertakings in international public health. Yet decision-makers are encountering significant uncertainties about financing and the need to understand programming costs at different scales of delivery.To review the economic methodologies for examining costs and variation by scale. To summarize and synthesize the current evidence related to the provision of HIV/AIDS interventions and scaling up.We used a review of economic methodologies to generate a conceptual framework for classifying existing data, looking at both short-run and long-run perspectives. A review of the literature was performed using PubMed and available grey literature. Factors facilitating comparison and generalizability are highlighted.There is growing evidence of scale variation among the costs of HIV/AIDS interventions. Scale variation has been found to explain 26–70% of cost variation across locations for similar interventions. Average costs may become larger or smaller as the volume of services expands, depending on the level of coverage and type of intervention. Key constraints to scaling up include infrastructure investments and cost results need to be interpreted in this light.Evidence to date suggests that cost efficiencies associated with scale may reflect different ways of delivering services at higher volumes, including lower quality outputs. There is still, however, an extremely limited economic evidence base and mechanisms to integrate economic analyses into routine programme monitoring are recommended.