Which studies should be registered on a clinical trials registry?

All Trials calls for all past and present clinical trials to be registered and their full methods and summary results reported. JAN requires that clinical trials are prospectively registered in a publicly accessible database such as and clinical trial registration numbers should be included in all papers that report their results. Authors are asked to include the name of the trial register and the clinical trial registration number at the end of the abstract. If the trial is not registered, or was registered retrospectively, the reasons for this should be explained.