  The progress in determining the coupling constants of mesonic chiral
Lagrangians is reviewed, with emphasis on the work performed in three
successive European Networks (Eurodaphne I and II, Euridice). Reliable
estimates of those constants are essential for making full use of
next-to-next-to-leading-order calculations in chiral perturbation theory. The
precision in the values of the strong coupling constants of O(p^4) has been
increasing steadily over the years. The situation is less satisfactory in the
nonleptonic weak sector where further phenomenological input and more
theoretical work are needed. A lot of progress has recently been achieved for
electromagnetic coupling constants occurring in radiative corrections for
mesonic processes at low energies.
