Background: Despite increasing emphasis on the use of research to inform decision making in health care there is concern that systematic reviews do not have the expected impact on policy and practice and more work may be needed to enable us to maximise their potential.

Objectives: The aim of this study was to increase understanding of the likely impacts of systematic reviews on policy and identify factors that might facilitate their influence.

Methods: Nine systematic reviews published between 1998 and 2008 and used established methods for the evaluation of research impact, including bibliometrics and documentary review, to examine whether or not these reviews had influenced policy development were reviewed. Data from these analyses were combined with an overview of the literature to identify factors that might increase impact.

Results: The reviews had influenced the development of national and international policy, although much of the impact was at a 'microá level in the form of guidelines for practice. There was considerable variation in the impact of the reviews. Reviews evaluating fluid resuscitation and road safety interventions showed the greatest evidence of impact, while a review of qualitative studies on barriers to fall prevention showed the least amount of impact. Differences might be explained by time since publication, type of question, importance to policy makers, the nature and strength of the evidence, the purpose of the review and the networks and strategies used for dissemination.

Conclusions: Systematic reviewers should consider the desired impacts of their work early in the review process and detail appropriate strategies for increasing impact in the review protocol. This might include specifying methods to address applicability to particular contexts and devising active strategies for dissemination.