- Sergei Haller (Giessen)
- Comp. group theory
- 18th Aug 2004 to 25th Sep 2004
- 11th Jan 2006 to 10th Oct 2006
- 16th Jan 2006 to 11th Jul 2007
- George Havas (UQ)
- Comp. group theory
- 10th Sep 1991
- 25th Nov 1991
- 6th Apr 1993 to 8th Apr 1993
- 23rd Sep 1997 to 28th Sep 1997
- 20th Dec 1998 to 23rd Dec 1998
- 9th Dec 2002 to 16th Dec 2002
- 16th Jul 2003 to 23rd Jul 2003
- 10th Jan 2012 to 17th Jan 2012
- Emanuel Herrman (Saarbruecken)
- Comp. number theory
- 15th Mar 1999 to 31st Dec 1999
- Florian Hess (TU Berlin)
- Comp. number theory, Cryptography
- 1st Oct 1999 to 30th Nov 2000
- 28th Feb 2005 to 10th Apr 2005
- James Hirschfield (Sussex)
- Finite Geometry
- 9th Dec 2005 to 5th Jan 2006
- 1st Apr 2011 to 30th Apr 2011
- 14th Dec 2013 to 12th Jan 2014
- Derek Holt (Warwick)
- Group Theory
- 1st Jan 1993 to 28th Feb 1993
- 18th Oct 1995 to 29th Nov 1995
- 20th Mar 1998 to 17th Apr 1998
- 22nd Oct 1999 to 17th Dec 1999
- 19th Oct 2002 to 13th Dec 2002
- 19th Mar 2005 to 16th Apr 2005
- 3rd Jan 2007 to 17th Mar 2007
- 3rd Oct 2009 to 5th Dec 2009
- 12th Jan 2012 to 10th Mar 2012
- 28th Sep 2014 to 3rd Dec 2014
- 23rd Jan 2017 to 10th Apr 2017
- 14th Mar 2019 to 17th Apr 2019
- David Howden (Warwick)
- Comp. group theory
- 13th Apr 2011 to 18th May 2011
