  We compute the real part of the 2-loop vertex corrections for charmless
hadronic B decays, completing the NNLO calculation of the topological tree
amplitudes in QCD factorization. Among the technical aspects we show that the
hard-scattering kernels are free of soft and collinear infrared divergences at
the 2-loop level, which follows after an intricate subtraction procedure
involving evanescent four quark operators. The numerical impact of the
considered corrections is found to be moderate, whereas the factorization scale
dependence of the topological tree amplitudes is significantly reduced at NNLO.
We in particular do not find an enhancement of the phenomenologically important
ratio |C/T| from the perturbative calculation.
