RESUMEN
Scientific journals represent the main disclosure tools for the advancement and development of Science. The importance of scientific journals can be usually defined in several ways including its prestige, which may be reflected in its citedness as measured by the impact factor (IF), which is a classic parameter useful to researchers. Due to controversial issues involving scientific publication, the purpose of this update article was to clarify and explain what is the impact factor of a journal and how it can guide faculty advisors and postgraduate students to publish their papers. The IF of a journal describes both journal and author impacts. It is based on two elements: the numerator, which is the number of citations in the current year to any items published in a journal in the previous two years, and the denominator, which is the number of substantive articles (source items) published in the same two years. Although IF is the only measure of journalÆs quality, it is important to remember that the calculation of the IF is biased by many factors. These include factors as inclusion of review articles, commentaries, errata and letters in numerator, but not in the denominator of the equation used to calculate the IF. Impact factor is the foremost tool to measure and indirectly indicate the research quality. Although it is not a perfect method and has several limited interpretation power, it remains a valuable measurement technique for scientific evaluation.