Duplicate publication is publication of a paper that overlaps substantially with one already published,without clear,visible reference to the previous publication.Prior publication may include release of information in the public domain.

Readers of medical journals deserve to be able to trust that what they are reading is original unless there is a clear statement that the author and editor are intentionally republishing an article （which might be considered for historic or landmark papers,for example）.The bases of this position are international copyright laws,ethical conduct,and cost-effective use of resources.Duplicate publication of original research is particularly problematic because it can result in inadvertent double-counting of data or inappropriate weighting of the results of a single study,which distorts the available evidence.

When authors submit a manuscript reporting work that has already been reported in large part in a published article or is contained in or closely related to another paper that has been submitted or accepted for publication elsewhere,the letter of submission should clearly say so and the authors should provide copies of the related material to help the editor decide how to handle the submission.

This recommendation does not prevent a journal from considering a complete report that follows publication of a preliminary report,such as a letter to the editor,a preprint or an abstract or poster displayed at a scientific meeting.It also does not prevent journals from considering a paper that has been presented at a scientific meeting but was not published in full,or that is being considered for publication in proceedings or similar format.Press reports of scheduled meetings are not usually regarded as breaches of this rule,but they may be if additional data tables or figures enrich such reports.Authors should also consider how dissemination of their findings outside of scientific presentations at meetings may diminish the priority journal editors assign to their work.

重復(fù)發(fā)表指發(fā)表與已發(fā)表論文內(nèi)容雷同的文章，而不清晰和明確地守用之前已發(fā)表的論文。

醫(yī)學(xué)期刊的讀者理當(dāng)相信他們所閱讀的是原創(chuàng)作品，除非有明確的說明指出作者和編輯特意再次發(fā)表某篇論文（例如可能被視為歷史性或里程碑式的文章）。這一立場是基于國際版權(quán)法、道德操守以及資源利用的成本效益。原創(chuàng)性研究的重復(fù)發(fā)表特別成問題，因為這會造成對單個研究的數(shù)據(jù)無意識地雙倍計數(shù)或不恰當(dāng)?shù)乜浯笤撗芯拷Y(jié)果的分量，從而歪曲現(xiàn)有的證據(jù)。

如果作者的投稿所報告的研究，大部分在某篇已經(jīng)發(fā)表的論文中報告過，或包含在已向他處投稿或已被接受將在他處發(fā)表的另一篇文章中，或與這樣一篇文章密切相關(guān)，則應(yīng)在投稿信中如實說明；而且，作者應(yīng)該提供相關(guān)材料的復(fù)印件，以便于編輯決定如何處理作者的投稿。

若已發(fā)表過初步報告，如致編輯的信、預(yù)印本、學(xué)術(shù)會議摘要或壁報等，此推薦規(guī)范不阻止期刊考慮發(fā)表其完整的報告。此推薦規(guī)范也不阻止期刊考慮發(fā)表在科學(xué)會議上報告過但尚未全文發(fā)表的文章，或擬安排在會議論文集中以摘要的形式發(fā)表的論文。對會期已定的學(xué)術(shù)會議的新聞報道通常并不被視為違反這一規(guī)則，但若附加圖表數(shù)據(jù)擴(kuò)充這種報道則另當(dāng)別論。作者還應(yīng)明白，以會議學(xué)術(shù)報告之外的方式傳播其研究結(jié)果可能有損編輯在期刊上發(fā)表其研究工作的優(yōu)先權(quán)。