Two years after instituting a policy that requires researchers to disclose information about current clinical trials in an online registry, editors of a dozen top medical journals have updated their rules.

The 12 influential journals include The Journal of the American Medical Association and The New England Journal of Medicine, which refuse to publish results of experiments that have not been previously registered in an online database. In a re-evaluation of their policy published today, the journals conclude, “The research community has embraced trial registration.”

Today’s update expands the scope of which trials must be registered. Starting in July 2008, the journals will require disclosure of so-called Phase I clinical trials, the small-scale, preliminary studies that look at the safety of experimental drugs or therapies, as well as larger studies.

The journal editors also note a push to require registration of trial results, not just the existence of trials. But many journals will not publish studies whose results have already appeared in print. The journal editors announced today that they would not consider results in online registries to be prior publication if they were kept to less than 500 words or were simply presented in the form of a table. —Lila Guterman