  The properties of the effective field theory relevant for the low energy
structure generated by the Goldstone bosons of a spontaneously broken symmetry
are reexamined. It is shown that anomaly free, Lorentz invariant theories are
characterized by a gauge invariant effective Lagrangian, to all orders of the
low energy expansion. The paper includes a discussion of anomalies and
approximate symmetries, but does not cover nonrelativistic effective theories.
