  The first part of this report reviews recent developments at the interface
between lattice work on QCD with light dynamical quarks, effective field theory
and low energy precision experiments. Then I discuss how dispersion theory can
be used to analyze the low energy structure of the $\pi\pi$ scattering
amplitude in a model independent manner. This leads to an exact formula for the
mass and width of the lowest few resonances, in terms of observable quantities.
As an application, I consider the pole position of the $\sigma$, paying
particular to error propagation in the numerical analysis. The report is based
on work done in collaboration with Irinel Caprini and Gilberto Colangelo.
