This International Standard applies to alpha/beta gas proportional counting systems used for the determination of the alpha-ray or beta-ray emission rates of radionuclides in sample counting. The intent is to establish standard methods for calibration and use of alpha/beta gas proportional counters, including measurement of their characteristics. Though principally applicable to beta-ray energies in excess of 100 keV, the techniques described in this standard are also useful for beta-ray energies at lower energies, provided a higher degree of care is taken with regard to sample preparation and calibration and measurement details.