In 2005, the International Committee of Medical Journal Editors (ICMJE) initiated a policy requiring investigators to deposit information about trial design into an accepted clinical trials registry before the onset of patient enrolment.1 This policy aimed to ensure that information about the existence and design of clinically directive trials was publicly available, an ideal that leaders in evidence based medicine have advocated for decades.2 The policy precipitated much angst among research investigators and sponsors, who feared that registration would be burdensome and would stifle competition. Yet, the response to this policy has been overwhelming. The ICMJE promised to re evaluate the policy two years after implementation. Here, we summarise that re-evaluation, specifically commenting on registries that meet the policy requirements, the types of studies that require registration, and the registration of trial results. As is always the case, the ICMJE establishes policy only for the 12 member journals (a detailed description of the ICMJE and its purpose is available at www.icmje.org), but many other journals have adopted our initial trial registration recommendations, and we hope that they will also adopt the modifications discussed in this update.

The research community has embraced trial registration. Before the ICMJE policy, ClinicalTrials.gov, the largest trial registry at the time, contained 13 153 trials; this number climbed to 22 714 one month after the policy came into effect.3 In April 2007, the registry contained over 40 000 trials, with more than 200 new trial registrations occurring weekly (D Zarin, personal communication). The four other registries that meet the ICMJE criteria have also grown as scores of journals have adopted the ICMJE clinical trials registration policy. In response to burgeoning registration, …