PRISMA: The PRISMA Group is a strong supporter of the AllTrials campaign. Too often, systematic reviews are concluded with statements like “more research is needed” and “the quality of studies is too poor to make a valid assessment of effect”. Often this happens because data in primary studies are so poorly reported or entire studies are missing from the scientific record, that researchers can’t make sense of the information at hand. This problem must end and the AllTrials initiative is a fundamental part of the solution.