Comprehensive reviews of the available research are generally considered to be the cornerstone of contemporary efforts to establish ‘evidence-based policy’. This article provides an examination of the potential of this stratagem, using the case study of ‘mentoring’ programmes. Mentoring initiatives (and allied schemes such as ‘coaching’, ‘counselling’, ‘peer education’ and so on) are to be found in every corner of public policy. Researchers have been no less energetic, producing a huge body of evidence on the process and outcomes of such interventions. Reviewers, accordingly, have plenty to get their teeth into and, by now, there are numerous reports offering review-based advice on the benefits of mentoring. The article asks whether the sum total of these efforts, as represented by five contemporary reviews, is a useful tool for guiding policy and practice. Our analysis is a cause for some pessimism. We note a propensity for delivering unequivocal policy verdicts on the basis of ambiguous evidence. Even more disconcertingly, the five reviews head off on different judgemental tangents, one set of recommendations appearing to gainsay the next. The article refrains from recommending the ejection of evidence baby and policy bathwater but suggests that much closer attention needs to be paid to the explanatory scope of systematic reviews.