  We discuss the status of different determinations of alpha_s, motivating a
precise and reliable computation from lattice QCD. In order to suppress
perturbative errors, the non-perturbative computation has to reach high energy
scales mu. Such results already exist in the SF-scheme for N_f=0,2 and N_f=3.
We recently added the running with four massless flavours in a range of alpha
from about 0.07 to 0.3 . It is based on our recent determination of the
Sheikholeslami Wohlert coefficient in the four-flavour theory.
