This paper identifies key barriers to the translation of science into practice and policy and makes recommendations for addressing them. It focuses on the challenges of translation within the field of tobacco control, but we argue that the insights are widely generalisable. Actor-Network Theory is used to frame an analysis, supplemented by focussed discussions with international tobacco control practitioners (service delivery and advocacy) and researchers. The central challenge to translation is that researchers and practitioners have different "practical ontologies". Researchers use findings from specific contexts to generalise to universal principles, while practitioners try to use these generalisations to inform their work in what are typically a somewhat different set of specific contexts. Neglecting the need to translate back from the general to the particular means research syntheses are not framed to meet practitioners' needs. Traditional knowledge broking roles need to be extended to better align the needs of researchers and practitioners. This may be facilitated by more creative use of "social computing" to enable real-time input into research syntheses from all interested parties, including input to the questions that research addresses. To do this systematically requires that we construct "generalisation gradients" to help practitioners apply general research conclusions to their particular situation and researchers to identify the relevance of their work. Disadvantaged communities in particular need help, since there is typically less research directly applicable to their contexts; thus, they need to generalise more.
Keywords: Action research; Actor-Network theory; Knowledge broking; Social computing; Tobacco control; Translational science.