Background: The CONSORT Statement provides recommendations for reporting randomized controlled trials. Objectives: We assessed the extent to which leading medical journals that publish reports of randomized trials incorporate the CONSORT recommendations into their journal and editorial processes. Methods: We report on two observational studies. Study 1: We examined the online version of "Instructions to Authors" for 165 high impact factor medical journals and extracted all text mentioning the CONSORT Statement or CONSORT extension papers. Any mention of ICMJE or clinical trial registration were also extracted. Study 2: We surveyed the editor-in-chief, or editorial office, for each of the 165 journals about their journal's endorsement of CONSORT recommendations and its incorporation into their editorial and peer-review processes. Results: Study 1: Thirty-eight per cent (62/165) of journals mentioned the CONSORT Statement in their online "Instructions to Authors"; of these 37% (23/62) stated this was a requirement, 63% (39/62) were less clear in their recommendations. Very few journals mentioned the CONSORT extension papers. Journals that referred to CONSORT were more likely to refer to ICMJE guidelines (RR 2.16; 95% CI 1.51 to 3.08) and clinical trial registration (RR 3.67; 95% CI 2.36 to 5.71) than those journals which did not. Study 2: Thirty-nine per cent (64/165) of journals responded to the online survey, the majority were journal editors. Eighty-eight per cent (50/57) of journals recommended authors comply with the CONSORT Statement; Sixty-two per cent (35/56) said they would require this. Fortyone per cent (22/53) reported incorporating CONSORT into their peerreview process and 47% (25/53) into their editorial process. Eighty-one per cent (47/58) reported including CONSORT in their "Instructions to Authors" although there was some inconsistency when cross checking information on the journal's website. Sixty-nine per cent (31/45) of journals recommended authors comply with the CONSORT extension for cluster trials, 60% (27/45) for harms and 42% (19/45) for non-inferiority and equivalence trials. Few journals mentioned these extensions in their "Instructions to Authors". Conclusions: Journals should be more explicit in their recommendations and expectations of authors regarding the CONSORT Statement and related CONSORT extensions papers.