  I review some aspects of the interplay between anomalies and chiral symmetry.
The quantum anomaly that breaks the U(1) axial symmetry of massless QCD leaves
behind a flavor-singlet discrete chiral invariance. When the mass is turned on
this residual symmetry has a close connection with the strong CP violating
parameter theta. One result is that a first order transition is usually
expected when the strong CP violating angle passes through pi. This symmetry
can be understood either in terms of effective chiral Lagrangians or in terms
of the underlying quark fields.
