Visiting Professor, Law School, University of Tilburg, The Netherlands, (1998-present); Visiting professor at the Economics Faculty of the University of Limburg, Belgium (2003 -2008)
Professor of Comparative Labour Law and Industrial Relations (1967-1998) and Dean, Law School, University of Leuven, Belgium (1984-1988);
Visiting Professor, Michigan State University (1970), University of Kentucky, (1976), INSEAD Fontainebleau (1981- ); Free University of Brussels (1985); Sophia University, Tokyo (1988), University of Florida (1989); University of Paris-Sorbonne (1993); Illinois (2000), K.U.Brussels (2006-2008), Modena (2008).
President of the Belgian Association of Industrial Relations (1967-1997).
President of the International Industrial Relations Association (1986-89); -President of the International Society for Labour and Social Security Law (2001- 2003)
Editor in Chief of the International Encyclopaedia for Labour Law and Industrial Relations (1975-present); the Bulletin of Industrial Relations;
General Editor of the International Encyclopaedia of Laws (1989-present); more than 1200 collaborators worldwide (www.ielaws.com)
Member of the Belgian Senate (1987- 1989).
Chairman of the Belgian Social Security Cross Point Data Bank (1990-1996);
Member of the Belgian Royal Academy of Sciences (1992-present);
President of the Alumni of the Law School, KULeuven, Belgium (1993-present);
Doctor honoris causa University of Szeged, Hungary (1997)
President of the Association of Scientific and Educative Authors (1997-present)
President of Reprobel, Belgian Society for Reprography (2001-2004; 2007-2010).