The editorial and peer-review processes should guarantee readers as to the reliability of published data. The first step of these processes is to check for errors. The aim of our study was to look for the presence of objective errors in consecutive articles published on three of the most authoritative clinical journals. Two reviewers evaluated the presence of any error in 200 consecutive original articles containing at least two tables, allowing a reanalysis of the data, published between October 2010 and April 2011. Error was considered any action different from what was planned. Errors were listed as: methodological, numerical and slips. They were considered as severe if numbers in the abstract were completely different from numbers reported in the full text. Among the 125 articles included in the study, 102 (82 %, 95 % CI 74-88 %) contained some kind of error, even multiple. Nine articles (7 %, 95 % CI 3-13 %) contained one slip, 92 articles (74 %, 95 % CI 65-81 %) contained at least one numerical error, and 22 articles (18 %, 95 % CI 11-25 %) contained one methodological error. Five articles (4 %, 95 % CI 1-9 %) contained one serious error. None of the errors retrieved (0 %, 95 % CI 0-2 %) would have changed the results of the studies. Most of the articles published in the most important medical journals present mistakes. Our results could be a clue to editorial and peer review systems system weaknesses. A debate within the scientific medical community about these systems, and possible alternative adjustments are needed.