Category theory is a mathematical discipline that is characterized by its role in unifying mathematics as well as its foundational vocation. Since it was created by Eilenberg and MacLane, its influence has grown both in breadth and depth. The history of its development is intimately linked to that of contemporary mathematics. Montreal has been an important research centre in category theory for more than 20 years. Research interests of the members include:

- algebra and topology;
- logic and the foundation of mathematics;
- theoretical computer science;
- mathematical linguistics.

The group is associated with the Category Theory Research Centre.

- Michael Barr (McGill)
- Luc Bélair (UQAM)
- Richard Blute (U. d'Ottawa)
- Michael Hallett (McGill, Philosophie)
- André Joyal (UQAM)
- M. Makkai (McGill)
- Jean-Pierre Marquis (U de M, Philosophie)
- Prakash Panangaden (McGill, Informatique)
- Ivo Rosenberg (U de M)
- Robert Seely (McGill)
- Phillip Scott (U. d'Ottawa)