Neutron nuclear data that is used in reactor dosimetry include thermal neutron cross sections and neutron resonance integrals for reactions on a target nucleus. Non-neutron nuclear data used in reactor dosimetry include isotopic compositions of target nuclides and radioactive half-lives, gamma-ray energies and intensities of reaction product nuclides. All of these data are periodically evaluated and recommended values are provided in the Handbook of Chemistry and Physics. The latest recommended values are discussed and they are contrasted with some earlier nuclear data, which were provided with neutron detector foils.