Systematic review and exploiting advances in SNA,58 further well designed research should examine the relationships between professionals’ network structures and health outcomes in a range of different care settings, and how the struc- tural aspects of health professional networks can be leveraged to improve quality of care and patient outcomes. As to limitations, like all systematic reviews, this review is bounded by its scope and the range and quality of the research we have been able to uncover. The grey literature was not included as it did not meet study inclusion criteria. It is challenging to draw together the lessons to be learnt from disparate studies, even those that share a common focus and methodology. CONCLUSION On the basis of this review, for those participating in or supporting networks, the lessons are threefold. First, understanding the structure and characteristics of professional networks is vital, and second, it is important to attend to how they function. This leads to a third lesson: it may be time well spent, depending on local conditions, to nurture professional networks, and invest the time to facilitate their contributions to care. For example, recent work by Meltzer et al59 demonstrates how SNA can assist in the design of effective quality improvement teams. The wellbeing of the organisation, the quality of services provided, and the collective efforts to deliver safe care to patients are likely to depend on such efforts. Spending time enabling networks is quite likely to be a useful pursuit for those intent on devel- oping sustainable and well functioning organisations. However, this is not guaranteed and even if progress can be made, it is likely to be time consuming with no assurance that the investment in energy and effort will realise improved systems, cultures and delivery systems. Our review has shown, nevertheless, that existing research provides a foundation for a potentially fruitful yet underexplored research agenda in ascertaining the worth of networks in improving clinical care. Acknowledgements We acknowledge the assistance, as second reviewer in the literature search, of Danielle Marks, Research Assistant, Centre for Clinical Governance Research, Australian Institute of Health Innovation, University of New South Wales, Sydney, Australia. Funding This study was funded by the Australian Research Council Discovery Project (ARC DP0986493) and in part by the National Health and Medical Research Council Program Grant (NHMRC 568612). ARC: funder of this study as part of overall project; NHMRC: funder of co-author, Jeffrey Braithwaite. Competing interests None. Contributors All authors contributed to the manuscript. 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