Author lists should inform readers about who did a piece of research. If authorship attribution is incorrect, the wrong people may take the credit or the blame. Correct authorship of medical papers is also important because the research and publication process relies on trust. If scientists or clinicians are prepared to lie about who was involved with a research project why should we believe their findings? Groups of journal editors, notably the International Committee of Medical Journal Editors, have tried to establish criteria for authorship but these are not universally accepted. Despite the lack of agreement, authorship of journal articles continues to be the basis for academic appointments and is used to measure the research output of departments and therefore determine future funding. Some journals have started to use contributor lists, indicating the role of each individual, in place of, or in addition to, traditional lists of authors. However, problems about the threshold of involvement that merits authorship, and the order of listing remain unresolved. Journal editors are usually unable to adjudicate on authorship disputes since detailed, local knowledge is required. Institutions might therefore play a greater role in setting and enforcing authorship policies. Disputes could be reduced if authorship criteria were agreed, in writing, among all contributors at the start of a research project.