Corrections of O(alpha(2)(S)) to the forward-backward asymmetry

We calculate the second-order QCD corrections to the forward-backward asymm etry in e(+)e(-) annihilation. Using the quark axis definition, we do not a gree with either existing calculation, but the difference relative to one o f them is small and understood. In particular, we point out that the forwar d-backward asymmetry of massive quarks is enhanced by logarithms of the qua rk mass. This implies that the forward-backward asymmetry of massless quark s is not computable in QCD perturbation theory and affected by non-power-su ppressed corrections coming from the non-perturbative fragmentation functio ns. We also calculate the second-order corrections using the experimentally -preferred thrust axis definition for the first time.