From the practicable viewpoint for environmental radioactivity measurement and monitoring, the liquid scintillation radioassay has been applied to low-level pure-beta and -emitter mixtures by using the most probable value theory. In low activity measurement, it is required to select a suitable emulsion scintillator and to deal with the calculated data statistically. Detection limit for a solution sample has been roughly estimated to be 10–2 Bq ml–1.