As social media and different forms of populism continue to undermine trust in top-down expertise, it’s clear that facts are coming under increasing pressure. But how are the effects of this being felt in health contexts, including the new conditions of COVID-19 ? What is happening to the idea of ‘evidence’? In what terms is it now asserted and contested? What forms does it take, how does it gain or lose authority, and how can we continue to use and mobilise it in relation to health matters? The Index of Evidence approaches these twenty-first century questions by repurposing a distinctly old-fashioned print device. It puts the alphabetical index to creative use as the starting point for a co-authored, open-ended and evolving text. While a definitive account of our current upheavals can’t yet be written, this index is instead a work in progress. It traces the shifting dynamics of evidence, mapping the connections between an emergent network of new concepts, terminologies and new ways of thinking.