  The next-to-next-to-leading order perturbative QCD corrections to R_tau and
the higher moments of the invariant mass distribution in the hadronic tau
decays are considered. The renormalization scheme dependence of these
corrections is discussed. The optimized predictions are obtained, using the
principle of minimal sensitivity as a guide to select the preferred
renormalization scheme. A simplified fit is performed, using R_tau and
R^12_tau, to see how the use of the optimized expansion may affect the
determination of the alpha_s and the dimension six condensates from the
experimental data.
