  The renormalization of chiral perturbation theory is carried out to
next-to-next-to-leading order in the meson sector. We calculate the divergent
part of the generating functional of Green functions of quark currents to
O(p^6) for chiral SU(n), involving one- and two-loop diagrams. The
renormalization group equations for the renormalized low-energy constants of
O(p^6) are derived. We compare our results with previous two-loop calculations
in chiral perturbation theory.
