“To assess quantitatively the completeness and clarity of author guidelines of international English-language journals in the biomedical and physical sciences, we randomly sampled 80 journals for which author guidelines were available online in English. The guidelines were reviewed for completeness and clarity in addressing ‘aims and scope,’ ‘submission and post-submission processes,’ ‘formatting instructions,’ ‘ethical requirements,’ and ‘authorship,’ and were subjectively assessed as being complete (score, 1) or incomplete (0), and clear (1) or unclear (0). Scores were represented as mean percentages. No journal scored 100% for completeness and clarity. ‘Formatting instructions’ was the most complete and clear category, and ‘authorship,’ the least complete and clear category. Biomedical science journals were more complete and clear in all categories, except ‘authorship,’ compared to physical science journals. While author guidelines of many English-language journals of biomedical and physical sciences adequately address some essential aspects, they currently do not provide all necessary information as clearly as possible. ”