“The case for registering all clinical trials—first advanced a decade ago1—is now unanswerable.”2 Editors of the BMJ and the Lancet made this statement in 1999. Five years of industry resistance, government impotence, and public confusion followed. Medical journals persisted with noble intentions and wise words but were themselves in part resistant, impotent, and confused about how to enforce registration. Some journals, including the BMJ, tried an amnesty for unpublished trials, with little success.3 The BMJ also considered asking for compulsory registration, but it seemed to us that trial registries were too diverse, disorganised, and easily disregarded to insist on registration before submission. Nor did we want fees for registering trials to be a barrier to researchers wanting to publish in the BMJ.

The world has changed. Undisclosed trials and duplicate and selective publication sting government agencies, clinicians, researchers, and journals ever more frequently and painfully. Crucially, this form of misconduct, which Iain Chalmers identified in 1990, distorts the scientific record.4 By suppressing negative findings and exaggerating positive ones, by downplaying harms and talking up benefits, healthcare decisions …