Research stays (CERN, Switzerland; Chalmers Technical Univ., Gothenborg, Sweden; FSU Tallahasse, USA; ZIF Bielefeld, Germany; UCSD, La Jolla, USA; HLRZ Jülich, Germany; Trinity Collage Dublin, Ireland); INT Univ. Washington, Seattle, USA. Head of the Inst. f. theoret. Physics (1988-1990, 1996-1998, 1999, 2001-2004). 1983-2014 I was leading the research group Lattice Quantum Field Theory. Vorsitzender der Studienkommission Physik (1999-2002) 1991-2015 I was Specialist Field Editor of Computer Physics Communications (North Holland). For the period 1994-1996 I was member of the Scientific Council of DESY (Deutsches Elektronen Synchrotron) and subpanels. 2005-2007 I was member of the Kuratorium of FWF (Fonds zur Förderung der Wissenschaftlichen Forschung in Österreich) 2012-2016 I was member of the SSC (Scientific Steering Committee) of PRACE (Partnership for Advanced Computing in Europe).