(Spain) Seminari de Teoria de Nombres de Barcelona (UPC)
- Members, research topics, publications, schedules.
- http://www-ma2.upc.edu/~quer/STNBUPC.html

(Singapore) National University
- Algebra and Number Theory Seminar. Schedule of meetings.
- http://www.math.nus.edu.sg/~mattankm/AlgSem/

(Canada) Queen's University, Kingston
- Algebra and Number Theory Group. Members, research interests.
- http://www.mast.queensu.ca/graduate/alge.php

(Germany) University of Siegen
- Algebra and Number Theory group. Members, research interests.
- http://wotan.algebra.math.uni-siegen.de/~countnumber/

(Germany) University of Regensburg/Leipzig
- Algebraic Cycles and L-Functions research group. People, preprints, seminars, workshops, positions, news.
- http://www.mathematik.uni-regensburg.de/FGAlgZyk/index-en.html

(Russia) Steklov Institute, Moscow
- Department of Number Theory. History, research projects, profiles.
- http://www.mi.ras.ru/departm/chisel_e.html

(USA) University of Rochester
- Algebra and Number Theory Group. Members, research interests, seminar schedule.
- http://www.math.rochester.edu/research/algebra_and_number_theory/

(UK) University of Glasgow
- Number Theory and Combinatorics. Staff, research interests.
- http://www.maths.gla.ac.uk/research/groups/ntc/

(Lithuania) Vilnius University
- Department of Probability Theory and Number Theory.
- http://www.mif.vu.lt/katedros/ttsk/home1.htm

(Germany) University of Heidelberg
- Algorithmic Algebra and Number Theory. Members, research, activities, software, links.
- http://www.iwr.uni-heidelberg.de/groups/compalg/

(Europe) Arithmetic Algebraic Geometry
- A European network of 12 working groups from 6 countries.
- http://www.arithgeom-network.univ-rennes1.fr/

(USA) New York Joint Number Theory Seminar
- Rotates between Columbia University, CUNY Graduate Center and NYU.
- http://math.gc.cuny.edu/seminars/jointnumbertheory.html

(Hungary) Lajos Kossuth University, Debrecen
- Department of Algebra and Number Theory. Staff list.
- http://www.math.klte.hu/algebra/indexa.htm

(Poland) Polish Academy of Sciences
- Department of Number Theory. Members, research interests, publications.
- http://www.impan.gov.pl/About/numberth.html

(Netherlands) CWI, Amsterdam
- Computational number theory group. Members, research interests, publications.
- http://db.cwi.nl/projecten/project.php4?prjnr=84

(USA) Southwestern Center for Arithmetical Algebraic Geometry
- Based at the University of Arizona, in collaboration with the Universities of New Mexico, Southern California, and Texas. Annual conference.
- http://swc.math.arizona.edu/

(China) Shandong University
- Number theory research group. Members, research interests, courses, events.
- http://www.prime.sdu.edu.cn/

(Italy) University of Pisa
- Number Theory Group. Research interests and members.
- http://www.dm.unipi.it/gauss-pages/melfi/public_html/

(Canada) University of British Columbia
- Number Theory group. Members, research areas and meetings.
- http://www.math.ubc.ca/~gerg/NT/

(USA) University of California Irvine
- Number theory seminar. Meetings, study groups, links.
- http://www.math.uci.edu/~chaessig/UCI_Number_Theory.html

(Ukraine) Tavrical National University
- Department of Algebra and Number Theory. Members, research interests, publications.
- http://www.ccssu.crimea.ua/eng/structure/math_fac/algebra.htm

(Japan) Okayama University
- Number Theory Group. Members.
- http://www.math.okayama-u.ac.jp/number.html

(Slovakia) Comenius University, Bratislava
- Department of Algebra and Number Theory. Research topics, contact information.
- http://www.uniba.sk/mffuk/e/departments/katc_e.htm

(Canada) University of Toronto
- Number Theory/Representation Theory Seminar. Schedule of meetings.
- http://www.math.toronto.edu/kc/ntrts/

(UK) University of Cambridge
- Number Theory Seminar. Meetings.
- http://www.dpmms.cam.ac.uk/Seminars/NumberT/

(Germany) Clausthal University of Technology
- Institut für Mathematik - Number Theory Research Group. People, research topics.
- http://www.math.tu-clausthal.de/Arbeitsgruppen/Zahlentheorie/Welcome_en.html

(UK) Cardiff University
- Number Theory Group. Members, research interests, advice to research students.
- http://www.cf.ac.uk/maths/numbertheory/

(Canada) CICMA, Concordia University, Montreal
- Number Theory Page. Members, seminars, preprints.
- http://cicma.mathstat.concordia.ca/number.html

(Croatia) University of Zagreb
- Seminar on Number Theory and Algebra. Members, seminars, links.
- http://www.math.hr/~duje/semeng.html

(Sweden) Uppsala University
- Mathematics III research group: quantum chaos and number theory.
- http://www.math.uu.se/research/iii/

(USA)University of Michigan
- Graduate Program in Number Theory. Staff, research interests, courses, seminars.
- http://www.math.lsa.umich.edu/research/number_theory/

(USA) University of California, Santa Barbara
- Arithmetic and Geometry Seminar. Meetings.
- http://www.math.ucsb.edu/~agboola/SGA.html

(Canada) McMaster University
- Algebra/Number Theory Seminar. Meetings, abstracts.
- http://icarus.math.mcmaster.ca/marshall/numbertheorySem.html

(UK) University of York
- Number Theory Research Group.
- http://www-users.york.ac.uk/~mmd1/numbertheory/

(USA) University of Wisconsin, Madison
- Algebra, Combinatorics and Number Theory Group. Members, seminars.
- http://www.math.wisc.edu/~ono/algebra.html

(Austria) Technical University of Graz
- Algorithmic and Probabilistic Number Theory Research Group. Members, research interests.
- http://finanz.math.tu-graz.ac.at/finanz/nth_eng.html

(Hungary) Alfréd Rényi Institute of Mathematics, Hungarian Academy of Sciences
- Number Theory research group staff.
- http://www.math-inst.hu/staff/number.html

(Germany) Technische Universität, Berlin
- Algebra and Number Theory: the KANT group. Members, software (KANT/KASH), publications.
- http://www.math.tu-berlin.de/algebra/

(Hungary) Eötvös University, Budapest
- Department of Algebra and Number Theory. Members pages.
- http://www.cs.elte.hu/algebra/

(Netherlands) University of Leiden
- Number theory research group. Staff, events, links.
- http://www.math.leidenuniv.nl/~desmit/numth/

(Finland) University of Turku
- Number Theory Group. Members, research interests.
- http://www.math.utu.fi/research/numbertheory/

(Austria) University of Vienna
- Johannes Schoißengeier's number theory research group. Members, research interests, links to other Austrian number theorists.
- http://radon.mat.univie.ac.at/Groups/Schoissengeier.html

(Austria) University of Natural Resources, Vienna
- Number theory group led by Werner Georg Nowak. Members, research interests, publications, links.
- http://www.boku.ac.at/math/nth.html

(USA) Penn State
- Algebra and number theory group. Members, seminars, preprints, links.
- http://www.math.psu.edu/vstein/alg/antheory/numtheory.html

(Russia) Steklov Institute, St. Petersburg
- Laboratory of Number Theory. Research interests.
- http://www.pdmi.ras.ru/lab/labnt.html

(USA) Boston University
- Algebra and Number Theory Research Group. Members, research interests, seminars, courses.
- http://math.bu.edu/research/algebra/

(South Africa) The John Knopfmacher Centre for Applicable Analysis and Number Theory, University of the Witwatersrand
- Members, research interests, preprints, meetings.
- http://www.wits.ac.za/science/number_theory/centre.htm

(USA) University of South Carolina
- Number Theory Group. Members, research interests, courses, links.
- http://www.math.sc.edu/~filaseta/numthry.html

(Europe) GTEM: Galois Theory and Explicit Methods in Arithmetic
- Research training network coordinated in Paris, uniting twelve teams from July 2000 until June 2004.
- http://www.math.jussieu.fr/~leila/gtem/gtem.html

(USA) University of California, Los Angeles
- Number Theory Group. Members, events, resources.
- http://www.math.ucla.edu/~ntg/

(USA) Texas A and M University
- Combinatorics/Number Theory Directory.
- http://www.math.tamu.edu/research/research_areas/cnt.html

(Israel) Ben Gurion University of the Negev
- Number Theory and Algebraic Geometry Research Group. Members, research interest, seminars.
- http://www.math.bgu.ac.il/~efrat/resgroup.html

(USA) University of Texas
- Number Theory Group. Members, meetings, software.
- http://www.ma.utexas.edu/~voloch/numberthy.html

(USA) Brown University
- Number Theory/Arithmetic Geometry Seminar. Members, meetings.
- http://www.math.brown.edu/~jhs/NTgroup.dir/NTgroup.html

(USA) University of Illinois at Urbana-Champaign
- Number Theory faculty, visitors, meetings, courses, events.
- http://www.math.uiuc.edu/ResearchAreas/NumberTheory/

(UK) Nottingham University
- Number Theory and Arithmetic Geometry research group. Research interests, members, visitors, meetings.
- http://www.maths.nott.ac.uk/personal/ibf/ntag.html

(UK) King's College, University of London
- Number Theory Group. Staff, meetings, preprints.
- http://www.mth.kcl.ac.uk/research/numbtheo/

(USA) University of Georgia
- Number Theory and Arithmetic Geometry Group. Members, seminars.
- http://www.math.uga.edu/~lorenz/Number_Theory_Group.html

(UK) University of Oxford
- Number Theory Group. Members, publications, meetings.
- http://www.maths.ox.ac.uk/ntg/

(UK) University of East Anglia
- Number Theory research.
- http://www.mth.uea.ac.uk/~h090/number_theory.html