Liquid scintillation counting (LSC) is a radiation measurement technique usually used for α- and β-emitters. A solution of a radionuclide is mixed with a so-called “scintillator cocktail”. By interaction of the ionizing radiation with the scintillator, UV light flashes are produced. These are eventually converted into electric impulses by photomultipliers. Due to the direct mixing of the radionuclide with the “detector”, thus removing any attenuation usually caused by a detector window and minimizing the source to detector distance, this method is especially suitable for measuring low level samples and low energy β- or E.C.-emitters with high efficiencies (>50%). By employing advanced efficiency calculation methods like CIEMAT/NIST or TDCR, radionuclide standardization is possible.