  We compute the dilatation generator in the su(2) sector of planar N=4 super
Yang-Mills theory at four-loops. We use the known world-sheet scattering matrix
to constrain the structure of the generator. The remaining few coefficients can
be computed directly from Feynman diagrams. This allows us to confirm previous
conjectures for the leading contribution to the dressing phase which is
proportional to zeta(3).
