  We describe KMS-states on the C*-algebras of etale groupoids in terms of
measurable fields of traces on the C*-algebras of the isotropy groups. We use
this description to analyze tracial states on the transformation groupoid
C*-algebras and to give a short proof of recent results of Cuntz, Deninger and
Laca on the Toeplitz algebras of the ax+b semigroups of the rings of integers
in number fields.
