La Universidad Nacional Autónoma de México tiene las siguientes funciones sustantivas: la docencia, la investigación y la difusión de la cultura. Sin embargo, hasta la fecha la Universidad no dispone de indicadores que den a conocer el grado de desarrollo al que ha llegado la investigación que se lleva a cabo en ella. Por tanto, se intentó determinar el desempeño de los investigadores universitarios en el periodo 1995-2003 a través de un análisis bibliométrico. Para la construcción de los datos empíricos se recurrió a la Web of Knowledge. Se identificaron 9903 artículos que lograron acumular 65291 citas, publicados la mayoría de ellos en disciplinas correspondientes a las ciencias duras. Se concluye que los investigadores de la UNAM tienen que esforzarse aún más para que la investigación se refleje en publicaciones que lleven a su incorporación a un mercado de la ciencia visible. / The National Autonomous University of Mexico has the following functions: teaching, research and popularization of culture. The University has been recognized by its outstanding performance and has been considered the most relevant institution of higher education at the national level and one of the best at the international level. However, so far, there are no indicators that show the direction into which the research activity is moving. Therefore, this investigation intended to determine the University's research performance from 1995 to 2003 using bibliometric techniques. The Web of Knowledge was used to identify cited papers and citations attracted. In order to determine the visibility of the communication channels used for the publication of research results, we used the Journal Citation Reports (JCR). We also tried to determine the global publication rate (GPR) of the researchers and an approximation of the cost of published articles by university departments.We identified 9903 articles that accumulated 65291 citations. We found that scientists in the hard sciences are more active and more cited than their colleagues in other areas. Three disciplines were the more active: space sciences, physics and microbiology.We concluded that researchers at the University have to work harder in order to be taken into account by the science that counts, i.e. the science that is visible.