Duplicate publication is publishing of an article that is identical to or overlaps considerable parts with one that has been already published elsewhere. If one or more authors retain common authorship in two separate papers with the same context, the papers are considered to be duplicated, but not plagiarized. The corresponding author was usually the case, but the first author is changed frequently. The characteristics of duplicate publication in Korea are republication of paper in journals indexed in SCI database after publishing in Korean journal one or two years before. In almost all cases they are not cross referenced. In Korean cases of duplicate publication, duplicate submissions are not rare. Generally the title is modified, and the list of authors and the sample size undergo a minor change with trivial methodological changes. Multiple publications in Korean journals usually consist of fragmentation (salami slicing) publications and overlapping (imalas) publications. Duplicate publication is an unethical behavior because of the waste of resources such as valuable time of busy reviewers, editorial work and pages, space of indexing database, and delaying the publication time of other researcher's paper. Duplicate publication is a violation of international copyright law as well. Sometimes it can distort or overemphasize the results in meta-analysis studies because of overlapping of samples. To prevent duplicate publication, the editor should provide instructions regarding the journal's policy toward duplicate publication and should make authors to read the instruction in detail. Educational programs for the reviewers will reduce the incidence by letting them know why and how to detect duplicate publication.