A process for hydrogenating aromatic di- and polyamines is provided comprising the steps of reacting the aromatic amine with hydrogen in the presence of a catalytic system, wherein the catalytic system comprises a heterogeneous catalyst comprising a metal selected from the group consisting of Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd and/or Pt and a support, and wherein the catalyst system further comprises an organic nitro compound. Hydrogenation of aromatic di- and polyamines having two or more amino groups bound to the aromatic ring produces cycloaliphatic di- and polyamines, which are useful chemical intermediates, e.g., for further reaction with epoxides or isocyanates. The amino groups may also be converted to isocyanates via reaction with phosgene. The resulting cycloaliphatic di- and polyisocyanates may also be used as monomers for making polymers.