Abstract A 35 group cross-section library with P3-anisotropic scattering matrices and resonance self-shielding factors has been generated from the basic ENDF/B-IV crosssection files for 57 elements. This library covers the neutron energy range from 0.005 ev to 15 MeV and is well suited for the neutronics and safety analysis of fission, fusion and hybrid systems. The library is contained in well known two files, namely, ISOTXS and BRKOXS. In order to test the efficacy of this library and to bring out the importance of resonance self-shielding, a few selected fast critical assemblies representing large dilute oxide and carbide fuelled uranium and plutonium based systems have been analysed. These assembliesinclude ZPR2, ZPR-3-48, ZPR-3-53, ZPR-6-6A, ZPR-6-7, ZPR-9-31 and ZEBRA-2 and are amongst those recommended by the Us Nuclear Data Evaluation Working Group for testing the accuracy of cross-sections. The evaluated multiplicatien constants of these assemblies compare favourably with those calculated by others.