  We review 3-transposition groups arising in vertex operator algebra theory.
One can construct a commutative algebra called the Matsuo algebra out of a
3-transposition group. Some 3-transposition groups arise as automorphism groups
of vertex operator algebras via Matsuo algebras but there exist some
3-transposition groups which do not arise through Matsuo algebras. We will
exhibit examples of those groups together with VOAs. This article is based on
the author's talk at the seminar on ``Majorana, Axial, Vertex Algebras and the
Monster (MAVAM)'' held online on June 4th, 2021.
