  The current state of knowledge of the order parameters of the spontaneously
broken chiral symmetry, the quark condensate and the pseudoscalar decay
constant in the chiral limit, is briefly reviewed, based on available
phenomenological fits and lattice QCD calculations. We argue that while the
theory is pretty well understood in the two-flavour case, there is still a gap
in the knowledge of the characteristics of the QCD vacuum in the three-flavour
one. Our constraints for the three-flavour parameters obtained by a Bayesian
statistical analysis of the decays of eta to three pions are presented.
Possible implications of a new analysis of subthreshold parameters of pion-pion
scattering is outlined.
