Until recently, the Zassenhaus Group Theory Conference merged with the Ohio State-Denison Mathematics Conference in even-numbered years, with the group theorists meeting in the odd-numbered years at various locations around the country. The even-numbered year conferences held in Ohio originally included group theory, ring theory, and combinatorics (areas in which Hans Zassenhaus was active). 

• 2018 - Zassenhaus Groups and Friends Conference, University of South Florida, Tampa, Florida: Abstracts + Program -- Group Photo -- Participant List
  
• 2017 - Zassenhaus Groups and Friends Conference, Binghamton University (SUNY), Binghamton, New York: Abstracts + Program -- Group Photo.
  
• 2016 - Zassenhaus Group Theory Conference, Adelphi University, Garden City, New York: Abstracts + Program -- Group Photo.
  
• 2015 - Zassenhaus Group Theory Conference, Binghamton University (SUNY), Binghamton, New York: Abstracts + Program -- Group Photo.
  
• 2014 - The XXXII^nd Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Abstracts + Program.
• 2013 - Zassenhaus Group Theory Conference, Western Carolina University, Asheville, North Carolina: Abstracts + Program -- Group Photo.
• 2012 - The XXXI^st Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Abstracts -- Schedule.
• 2011 - Zassenhaus Group Theory Conference, Towson University, Towson, Maryland: Abstracts + Program.
• 2010 - The XXX^th Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Abstracts +Program.
• 2009 - Zassenhaus Group Theory Conference, Franklin and Marshall College, Lancaster, Pennsylvania: Abstracts + Program.
• 2008 - The XXIX^th Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Abstracts + Program.
• 2007 - Zassenhaus Group Theory Conference, St. Louis University, St. Louis, Missouri: Abstracts + Program.
• 2006 - The XXVIII^th Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio.
• 2005 - Zassenhaus Group Theory Conference, Auburn University Montgomery, Montgomery, Alabama: Abstracts + Program -- Group Photo.
• 2004 - The XXVII^th Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio.
• 2003 - Zassenhaus Group Theory Conference, University of Evansville, Evansville, Indiana: Abstracts + Program.
• 2002 - The XXVI^th Ohio State-Denison Mathematics Conference, Denison University, Granville, Ohio.
• 2001 - Zassenhaus Group Theory Conference, New College of USF, Sarasota, Florida -- Group Photo.
• 2000 - The XXV^th Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio.
• 1999 - Groups 99: The Zassenhaus Group Theory Conference, Binghamton University, Binghamton, New York: Abstracts + Program -- Schedule -- Group Photo.
• 1998 - The XXIV^th Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio.
• 1997 - Zassenhaus Group Theory Conference, New College of USF, Sarasota, Florida.
• 1994 - The XXIInd Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Program
• 1993 - Zassenhaus Group Theory Conference, Binghamton University (SUNY), Binghamton, New York: Program
• 1992 - The XXIst Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Program
• 1988 - The XXth Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Program
• 1987 - The Regional Conference on Group Theory, The University of Pittsburgh, Pittsburgh, Pennsylvania: Program
• 1985 - The Regional Conference on Group Theory, The University of Pittsburgh, Pittsburgh, Pennsylvania: Program
• 1984 - The XVIIth Ohio State-Denison Mathematics Conference, The Ohio State University, Columbus, Ohio: Program
• 1983 - The 1983 Annual Regional Conference on Group Theory, The University of Pittsburgh, Pittsburgh, Pennsylvania: Program
  
• 1981 - The XVIth Ohio State-Denison Mathematics Conference, Denison University, Granville, Ohio: Program
• 1980 - The XVth Ohio State-Denison Mathematics Conference, Denison University, Granville, Ohio: Program
• 1979 - The XIVth Ohio State-Denison Mathematics Conference, Denison University, Granville, Ohio: Program
• 1971 - The 10th Denison Conference in Group Theory, Lie Algebras, and Algebraic Geometry, Denison University, Granville, Ohio: Program
• 1969 - The 9th Denison Mathematical Conference, Denison University, Granville, Ohio: Program
  

The Ohio State University Department of Mathematics maintains a website with more information about the life and work of Hans Zassenhaus, as does MacTutor History of Mathematics Archive.