  We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant
baryon chiral perturbation theory. We present a calculation of pion photo- and
electroproduction up to and including order $q^4$. The low-energy constants
have been fixed by fitting experimental data in all available reaction
channels. Our results can be accessed via a web interface, the so-called chiral
MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/).
