This article addresses the synthesis and use of research evidence to inform policy and practice. Reviews of the evidence base in many fields have formed a crucial bridge between research, policy making and practice. Systematic review, in conjunction with meta-analysis, has become an established methodology for locating, selecting, appraising and quantitatively synthesising research evidence according to an explicit and reproducible methodology. However, the ‘standard’ systematic review template associated with the Cochrane Collaboration is often criticised for its perceived inability to cope with variation in study design, nature of evidence and study context. We present five approaches to research synthesis, conducted in different fields, using contrasting methodologies. A number of methodological, practical and strategic implications of conducting research syntheses are explored. The article aims to stimulate debate about what counts as good-quality synthesis, and to demonstrate the growing diversity in its practice. In so doing, the article offers researchers and commissioners a range of approaches to producing reviews of the evidence base.