Holmium-166m was obtained by irradiation of metallic holmium in a high-flux nuclear reactor. It was separated from rare-earth impurities and other accompanying radionuclides by extraction chromatography on a column using 1.95 M nitric acid as an eluent. The specific activity of the 166m Ho was 1.3 mCi/g Ho. The effective burn-up cross-section for 166m Ho was found to be 7500 barn. The activity standardization of the 166m Ho was carried out by extrapolation of the 4π (β, e)-γ coincidences. The absolute and relative γ-ray intensities for the 32 γ-ray energies emitted in the 166m Ho decay have been measured.