In the early days of randomised clinical trials, their results could be manipulated in several ways—protocols could be altered in light of early findings, sponsors could exert undue influence over what could be published, and some “unfavourable” results could be suppressed entirely. In the United States, the creation of the government clinical trials website (www.clinicaltrials.gov) greatly contributed to minimising these threats to honest science.1 But requiring similar consistency, rigour, and transparency has been more difficult with observational studies, because any person or company with modest resources can purchase a large database of health insurance claims and perform a variety of epidemiological analyses with little or no accountability for the transparency, rigour, or visibility of such work⇓.

In 2006, the European Medicines Agency took on this problem by creating the European Network of Centres for Pharmacoepidemiology and Pharmacovigilance (ENCePP) to provide registration, standardisation, and quality assurance for observational studies of the effects of drugs (www.encepp.eu/). To qualify for the “ENCePP seal,” study organisers must agree to a code of conduct and transparency, meet a checklist of methodological standards, and agree to publicly post the study protocol as well as its results.2

“Best practices” for the conduct of epidemiological studies of the safety of drugs are less well standardised than those developed over the …