  The one-loop dilatation operator in Yang-Mills theory possesses a hidden
integrability symmetry in the sector of maximal helicity Wilson operators. We
calculate two-loop corrections to the dilatation operator and demonstrate that
while integrability is broken for matter in the fundamental representation of
the SU(3) gauge group, for the adjoint SU(N_c) matter it survives the conformal
symmetry breaking and persists in supersymmetric N=1, N=2 and N=4 Yang-Mills
theories.
