  Using non relativistic effective Lagrangian techniques, we analyze the
hadronic decay of the pi+pi- atom and the strong energy-level shift of pionic
hydrogen in the ground state. We derive general formulae for the width and
level shift, valid at next-to-leading order in isospin breaking. The result is
expressed in terms of hadronic threshold amplitudes that include
isospin-breaking effects. In order to extract isospin symmetric scattering
lengths from the data, we invoke chiral perturbation theory, that allows one to
relate the scattering lengths to the threshold amplitudes.
