In Greece, power stations burning lignite from two large deposits, in the regions of Megalopolis and Ptolemais, play an important role in meeting the electric energy needs of the country. The investigation reported here deals with the determination of the 226Ra, 228Ra and 40K concentrations in the lignite feeding two power units in Megalopolis and in the product ash. Systematic sampling allowed evaluation of mean representative concentrations and estimation of the resulting atmospheric discharges of radioactivity. Furthermore, statistical analysis has shown that, at the 95% confidence level, essentially all 226Ra from the lignite feeding each unit is accounted for in the ash. The results of both the present and previous investigations on two units burning lignite from the Ptolemais deposit show that electricity generation from Greek lignites is associated with radioactivity discharges which are rather high relative to corresponding discharge data from the literature.