  We report on recent progress on the flavour non-singlet splitting functions
in perturbative QCD. The~exact four-loop (N^3LO) contribution to these
functions has been obtained in the planar limit of a large number of colours.
Phenomenologically sufficient approximate expressions have been obtained for
the parts not exactly known so far. Both cases include results for the
four-loop cusp and virtual anomalous dimensions which are relevant well beyond
the evolution of non-singlet quark distributions, for which an accuracy of
(well) below 1% has now been been reached.
