The thermal neutron cross section and the resonance integral of the reaction Ho-165-(n, gamma)(166)gHo were measured by the activation method using Mn-55(n,gamma)Mn-56 monitor reaction. The sufficiently diluted MnO2 and Ho2O3 samples with and without a cylindrical Cd case were irradiated in an isotropic neutron field of the Am-241-Be neutron sources. The gamma-ray spectra from the irradiated samples were measured with a calibrated n-type high purity Ge detector. Thus, the thermal neutron cross section for Ho-165(n, gamma)Ho-166g reaction has been determined to be 59.2 +/- 2.5 b relative to the reference thermal neutron cross section value of 13.3 +/- 0.1 b for the Mn-55(n, gamma)Mn-56 reaction, and it generally agrees with the recent measurements within about 1 to 12%. The resonance integral has also been measured relative to the reference value of 14.0 +/- 0.3 b for the Mn-55(n gamma)Mn-56 reaction using an epithermal neutron spectrum of the Am-241-Be neutron source. The resonance integral for Ho-165(n, gamma)Ho-166g reaction obtained was 667 +/- 46 b at a cut-off energy of 0.55 eV for 1 mm Cd thickness. The existing experimental and evaluated data for the resonance integral are distributed from 618 to 752 b. The present resonance integral value agrees with most of the previously reported values obtained by (197)An standard monitor within the limits of error. (C) 2004 Elsevier Ltd. All rights reserved.