  We report on the non-perturbative computation of the running coupling of
two-flavour QCD in the Schr"odinger functional scheme. The corresponding
Lambda-parameter, which describes the coupling strength at high energy, is
related to a low energy scale which still remains to be connected to a hadronic
``experimentally'' observable quantity. We find the non-perturbative evolution
of the coupling indispensable to avoid untolerable errors in the estimated
Lambda-parameter.
