Director of CWTS and professor of Scientometrics at Leiden University (from 1 September 2010).
Special professor of Knowledge Dynamics at the Erasmus University Rotterdam (from 1 November 2007). Visiting professor of Cybermetrics at the University of Wolverhampton (since April 2006).
Programme Leader of the Virtual Knowledge Studio for the Humanities and Social Sciences (Royal Netherlands Academy of Arts and Sciences) (2006 - 2010). Director of the Erasmus Virtual Knowledge Studio KNAW (2006 - 2010). Programme Leader of Networked Research and Digital Information (Nerdi) at the Royal Netherlands Academy of Arts and Sciences (2000-2005).
Coordinator of the Graduate School WTMC (Science, Technology, and Modern Culture) (together with Dr. Annemiek Nelis) (2001 - 2004).
Editor of the bimonthly professional journal Onderzoek Nederland (1998 - 2005).