  A way to explain the puzzling difference between the pion form factor as
measured in e+ e- annihilations and in tau decays is discussed. We show that
isospin symmetry breaking, beside the already identified effects, produces also
a full mixing between the rho0, omega and phi mesons which generates an isospin
0 component inside the rho0 meson. This effect, not accounted for in current
treatments of the problem, seems able to account for the apparent mismatch
between e+ e- and tau data below the phi mass.
