The neutron average total cross section of thorium has been measured near 24 keV in an accurate transmission experiment using the time-of-flight method and the iron-filtered-beam technique. The measured average total cross section is 14.933 ± 0.041 b. The computer codes BABEL and MCROSS were used to stochastically calculate average cross sections near 24 keV from several sets of resonance parameters. The average total cross section calculated from the Forman et al. data set is in good agreement with the experimental results, but the cross section calculated from the ENDF/B-IV data set is 16% lower than the measured value. The major part of this 16% discrepancy is attributed to too small a nuclear scattering radius in the ENDF/B-IV data set.