Publications are primarily a means of communicating scientific information to colleagues, but they are much more than that. Publications in peer reviewed journals are proof of academic competence, are used as a crucial component in evaluation criteria for academic promotion and fundraising and increase the prestige of research centres and universities. The urgent need for publications has also led to abuses in authorship. In the past the single-author article was the rule, but over the past decades, the average number of authors on scientific manuscripts has drastically increased. In the field of bioethics, however, no research has been undertaken to study whether the percentage of single-author articles is decreasing, the proportion of multi-author articles is increasing or the average number of authors per article is increasing. The objective of this research is to analyze these trends in authorship for the period 1990-2003 in peer reviewed journals in the field of bioethics. In the nine peer reviewed journals from the field of bioethics we studied, we observed a significant increase of the multi-author article and of the average number of authors. This is mainly due to the increase in the number of publications with an empirical design. This growing trend is a challenge for the editors of journals in the field of bioethics to enhance awareness about the value and definition of authorship.