  Using a combination of {\it ab initio} bandstructure methods and dynamical
mean-field theory we study the single-particle spectrum of the prototypical
charge-transfer insulator NiO. Good agreement with photoemission and
inverse-photoemission spectra is obtained for both stoichiometric and
hole-doped systems. In spite of a large Ni-$d$ spectral weight at the top of
the valence band the doped holes are found to occupy mainly the ligand $p$
orbitals. Moreover, high hole doping leads to a significant reconstruction of
the single-particle spectrum accompanied by a filling of the correlation gap.
