The evidence-based policy approach – the view that social policy ought to be based upon supporting evidence that the policy works (and why it works) – is currently in vogue. In this article we reflect upon one aspect of the evidence-based approach: the use of quantitative evidence in health care decision-making. In particular, we discuss both the potential usefulness of quantitative evidence in this context, and the barriers to the appropriate use of such evidence at the decision-making level.