Covers radionuclide calibrators of the well type, with a gas-filled ionization chamber as used in the practice of nuclear medicine. The object of this Standard is to identify the most important characteristics of radionuclide calibrators and lay down associated test methods to enable manufacturers to declare the characteristics of their devices in a standardized way and facilitate comparisons between devices. The contents of the corrigendum of June 2016 have been included in this copy.