Factorial trials, in which two or more interventions are simultaneously evaluated, have specific design and analysis considerations not covered by standard SPIRIT and CONSORT statements. Reviews show that the reporting quality of factorial trials is often poor. The RAFT (Reporting Factorial Trials) study will develop SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) and CONSORT (Consolidated Standards of Reporting Trials) extensions for the reporting of factorial trials.