QCD perturbation theory at low energies.

We apply the optimization procedure based on the principle of minimal sesitivity to the third-order calculation of ${\mathit{R}}_{\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$. The effective couplant remains finite, freezing to a value ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$/\ensuremath{\pi}=0.26 at low energies. Using Poggio-Quinn-Weinberg smearing we find good agreement between theory and experiment right down to zero energy.