[en] Neutron nuclear data of ²⁵²Cf and ²⁵⁰Bk have been evaluated in the neutron energy range from 10^-5 eV to 20 MeV. The cross sections evaluated are the total, elastic and inelastic scattering, (n, 2n), (n, 3n), (n, 4n) reaction, fission and capture cross sections. For the both nuclides, cross sections below 30 keV were represented with resolved and unresolved resonance parameters. For ²⁵²Cf, the resolved resonance parameters were evaluated in the energy range from 10^-5 eV to 1 keV and the unresolved resonance parameters above 1 keV. For ²⁵⁰Bk, no resonance parameters have been reported. Therefore, hypothetical resolved resonance parameters were given below 100 eV. In addition, angular and energy distributions of emitted neutrons and average number of emitted neutrons per fission were also evaluated. Existing experimental data are only those for the fission cross section of ²⁵²Cf, thermal cross sections and resonance integrals of ²⁵²Cf and the fission cross section of ²⁵⁰Bk at the thermal neutron energy. The present evaluation, therefore, was mainly based on the systematics of the data from neighboring nuclides and optical- and statistical-model calculations. (author)