Continuous-trace groupoid C^-algebras. III

Suppose that {\groupoidfont G} is a second countable locally compact groupoid with a Haar system and with abelian isotropy. We show that the groupoid C^{\displaystyle *}-algebra \mathcs({\groupoidfont G},\lambda) has continuous trace if and only if there is a Haar system for the isotropy groupoid {\groupoidfont A} and the action of the quotient groupoid {\groupoidfont G}/{\groupoidfont A} is proper on the unit space of {\groupoidfont G}.