This document applies to liquid scintillation counters and requires the preparation of a scintillation source. The scintillation source is obtained by mixing the test sample and a scintillation cocktail. The test sample can be liquid (aqueous or organic), or solid (particles or filter or planchet). NOTE Planchet are samples, described in 8.5, out of solid material e.g. small metal, plastic or glass pans or support material made of these materials This document describes the conditions for measuring the activity of beta emitter radionuclides by liquid scintillation counting[2][3]. The choice of the test method using liquid scintillation counting involves the consideration of the potential presence of other beta-, alpha- and gamma emitter radionuclides in the test sample. In this case, a specific sample treatment by separation or extraction is implemented to isolate the radionuclide of interest in order to avoid any interference with other beta-, alpha- and gamma-emitting radionuclides during the counting phase. This document is applicable to all types of liquid samples having an activity concentration ranging from about one Bq·l−1 to 106 Bq·l−1. For a liquid test sample, it is possible to dilute liquid test samples in order to obtain a solution having an activity compatible with the measuring instrument. For solid samples, the activity of the prepared scintillation source shall be compatible with the measuring instrument. The measurement range is related to the test method used: nature of test portion, preparation of the scintillator - test portion mixture, measuring assembly as well as to the presence of the co-existing activities due to interfering radionuclides. Test portion preparations (such as distillation for 3H measurement, or benzene synthesis for 14C measurement, etc.) are outside the scope of this document and are described in specific test methods using liquid scintillation[4][5][6][7][8][9][10][11].