Abstract

We show that every groupoid C*algebra is isomorphic to its opposite, and
deduce that there exist C*algebras that are not stably isomorphic to groupoid
C*algebras, though many of them are stably isomorphic to twisted groupoid
C*algebras. We also prove that the opposite algebra of a section algebra of a
Fellbundle over a groupoid is isomorphic to the section algebra of a natural
opposite bundle.