Precise Determinations of the Strong Coupling Constant

Recent results for the cross section of electron-positron annihilation into hadrons and for the decay rates of the Z-boson and the τ-lepton into hadrons including corrections of order are reviewed. The consistency between two values of αs measured at vastly different energies constitutes a striking test of asymptotic freedom. Combining the results from Z and τ decays we find αs(MZ)=0.1198±0.0015 as one of the most precise and presently only NNNLO result for the strong coupling constant.