The document specifies the determination of radium-226 (226Ra) and radium-228 (228Ra) activity concentrations in drinking water samples by chemical separation of radium and its measurement using liquid scintillation counting. 226Ra and 228Ra are present in the environment as radionuclides from the 238U and 232Th decay series, as shown in Annex A. The test method applies to the analysis of 0,5 kg of drinking water containing less than 100 mg/kg barium. If the barium concentration is higher than 100 mg/kg, it is recommended to reduce the volume of the test sample to be analysed so that the total content of barium in the sample does not exceed 50 mg. Activity concentrations of 226Ra and 228Ra can vary widely according to local geological and climatic characteristics. 226Ra activity concentration range from some mBq/l in surface waters up to several tens of Bq/l in some natural groundwaters[8]; the guidance level for 226Ra in drinking water as recommended by WHO is 1 Bq/l[3][9]. 228Ra activity concentration range from a few mBq/l in surface waters up to several Bq/l in some natural groundwaters[8]; the guidance level for 228Ra in drinking water as recommended by WHO is 0,1 Bq/l[3][9]. Activity concentrations of 226Ra and 228Ra which can be measured by this test method utilizing currently available liquid scintillation counters goes down to 0,01 Bq/kg for 226Ra and 0,06 Bq/kg for 228Ra for a 0,5 kg sample mass and a 1 h counting time in a low background liquid scintillation counter.[10] NOTE Adjustment of the test sample mass and counting time can lead to lower detection limits. As an example, a limit of detection of 0,04 Bq/kg can be achieved for 228Ra using a 0,5 kg test sample and a 2 h counting time; similarly a limit of detection of 0,02 Bq/kg can be achieved for 228Ra using a 1 kg test sample and a 2 h counting time. The test method can be used for the fast detection of contamination of drinking water by radium in emergency situations or for routine environmental monitoring purposes.