This International Standard specifies a method for the determination of gross alpha and gross beta activity concentration for alpha- and beta-emitting radionuclides. Gross alpha and gross beta activity measurement is not intended to give an absolute determination of the activity concentration of all alpha and beta emitting radionuclides in a test sample, but is a screening analysis to ensure particular reference levels of specific alpha and beta emitters have not been exceeded. This type of determination is also known as gross alpha and beta index. Gross alpha and beta analysis is not expected to be as accurate nor as precise as specific radionuclide analysis after radiochemical separations. Maximum beta energies of approximately 0,3 MeV or higher are measured. Low energy beta emitters (e.g. 3H, 228Ra, 210Pb, 14C, 35S, and 241Pu) may not be detected. The method covers non-volatile radionuclides, since some gaseous or volatile radionuclides (e.g. radon and radioiodine) may be lost during the source preparation. The method is applicable to test sample of drinking water, rainwater, surface and ground water as well as cooling water, industrial water, domestic and industrial wastewater after proper sampling, sample handling, and test sample preparation (filtration when necessary and taking into account the amount of dissolved material in the water). The method described in this standard is applicable in the event of an emergency situation, because the results can be obtained in less than 1 h. It is the laboratory s responsibility to ensure the suitability of this test method for the water samples tested.