Medical journals are often at risk of difussing research articles, reviews, position articles, editorials or letters whose message has been influenced by a conflict of interest. The readers may then be induced to accept conclusions and recommendations based on biassed protocols or an unwarranted interpretation of the results. Financial support or professional links with pharmaceutical companies or other supporting agencies are the most common sources of conflict of interests, often difficult to detect. Similarly, reviews of manuscripts can be biassed by personal relationships (good or bad) between reviewers and authors, by academic competition or intellectual passion, becoming other sources of conflict of interest. Even when a potential conflict of interest exists, it may not necessarily have influenced the manuscript or its review but in order to defend the transparency of the editorial process, from submission to publication, authors, reviewers and editors should declare any conflict of interest they may have and allow others to decide whether the action has been biassed or not. In the present issue of Revista Médica de Chile, an updated text of the Instructions to Authors establishes that all authors should sign a statement of having or not a conflict of interest, clarifying which aspects of the work might have been affected by it (Rev Med Chile 2003; 131: 7-9)