In this work radiative corrections in the total hadronic decay rate of
the tau-lepton and some moments of its differential distributions are
studied employing perturbative QCD and the operator product expansion.
We calculate quadratic quark mass corrections in the strange mass to
the decay rate ratio R_{\tau} to the order
O(\alpha_s^3 m^2) and find that they contribute appreciably
to the Cabibbo suppressed decay modes of the $\tau$-lepton.
Using the results of a recent experimental analysis, we obtain
m_s(1 GeV ) = 200 \pm 40_{exp} \pm 30_{th} MeV.
