Each clinical trial must have a unique trial number and be registered on a publicly accessible database. Trial registration helps researchers fulfil research transparency and result dissemination requirements and is a condition of favourable ethics opinion (unless a deferral of registration has been granted). Many publishers, including the International Committee of Medical Journal Editors (ICMJE), require registration as a pre-condition of publication.

Unique trial number. We recognise the need for a unique number to be used to
identify each trial in protocol and results registers and publications. However the
benefit of creating and assigning an additional, WHO generated, universal trial
reference number (in addition to that assigned by the primary register) is not apparent
(see Appendix 1).