OBJECTIVE To assess financial, nonfinancial and editors' conflicts of interest (COI) disclosure policies among the most influential biomedical journals publishing original research. METHODS We conducted a cross-sectional study of 399 high-impact biomedical journals in 27 biomedical categories of the Journal Citation Reports (JCR) in December 2011. Information relevant to COI and requirements for disclosures that was publicly available on journal websites was collected. RESULTS While financial COI disclosures were required by 358 (89.7%) and nonfinancial by 280 (70.2%) journals, 155 (38.8%) required editors' disclosures. Journals in the first decile of the JCR classification scored significantly higher than those in the second decile for all disclosure policies. Ninety (22.6%) journals were published by Elsevier and 59 (14.8%) by Wiley-Blackwell, with Elsevier scoring significantly better in financial disclosure policies (P = 0.022). Clinical journals scored significantly higher than basic journals for all disclosure policies. No differences were observed between open-access (n = 25) and nonopen-access (n = 374) journals for any type of disclosure. Somewhat incoherently, authors' disclosure statements were included in some published manuscript in 57.1% of journals without any COI disclosure policies. CONCLUSIONS Authors' financial COI disclosures were required by about 90% of high-impact clinical and basic journals publishing original research. Unlike recent studies showing a significantly lower prevalence of nonfinancial compared with financial disclosures, the former were required by about 70% of journals, suggesting that editors are increasingly concerned about nonfinancial competing interests. Only 40% of journals required disclosure of editors' COI, in conflict with the recommendations of the most influential editors' associations.