An experimental investigation of the total neutron cross section for natural carbon was made at Kyiv Research Reactor using neutron-filtered beams with energies 24, 59, and 148 keV. The intense neutron beams formed by composite neutron filters at reactor horizontal channels )had fluxes of about 106 to 107 neutron/cm2 s at the fixed neutron energies, which enabled us to measure the neutron cross sections with accuracy better than 1 %. Transmission method was used in these measurements. The results of the measurements are presented together with the analysis of the known previous experimental data and the evaluated nuclear data from ENDF libraries. Sample thickness dependence of the observed neutron cross section, measured at the 148-keV filter, has been detected which hypothetically may be connected with existence of a very strong resonance in the 13C neutron cross section in the energy range 119 to 157 keV.