Authorship of a scientific paper is important in recognition of one's work, and in the academic setting, helps in professional promotion. Conflicting views of authorship have led to disputes and debates in many scientific communities. Addressing ethical issues in medical research and publishing, and conforming to the requirements of international organizations and local research ethics boards (REBs), has become an essential part of the research endeavor. Ethical issues of biomedical authorship have been a matter of debate for years. Authorship problems may involve problems with integrity, including ghost authorship and guest authorship. Some scientific disciplines, such as engineering or social sciences, may not have a firm guideline for authorship criteria; however this article reviews the criteria of authorship recommended by related international organizations of biomedical field and discusses common scenarios that may lead to authorship disputes and misconducts as well as issues related to authorship in multicenter studies. The paper also discusses possible scenarios that might be legitimate to make changes in authorship lists.