  We consider chiral perturbation theory in the meson sector at order $E^6$. In
the terminology of the external field technique, the two--loop graphs so
generated are of the sunset type. We discuss the evaluation of several of these
in the case where the masses of the particles running in the loops are equal.
In particular, we present integral representations that are suitable for the
evaluation of diagrams in kinematical regions where branch points and cuts are
present.
