  Chiral symmetry serves as a guiding principle in low-energy hadron dynamics.
An effective lagrangian, which explicitly breaks chiral symmetry via a small
mass term, allows for a systematic method of calculating higher order
corrections to tree-level results. This is applied to radiative muon capture on
hydrogen, %to extract the weak pseudoscalar form factor, and to proton-proton
$\pi^0$ production near threshold. Both processes pose theoretical challenges
in light of recent experimental results.
