Excretion rates of (210)Po and (210)Pb in the urine were investigated in 40 healthy inhabitants of Prague (22 males, 18 females, age: 23-70 y, non-smokers). In 20 inhabitants the excretion rates of (210)Po and (210)Pb in faeces were also studied. The mean urinary excretion rates of (210)Po and (210)Pb were 4.1 and 6.0 mBq d(-1), respectively. It was demonstrated, statistically, that the urinary excretion rates of (210)Po and (210)Pb are higher in men than those in women. The highest excretion rates of (210)Po and (210)Pb found in the participants were 10.8 and 16.6 mBq d(-1), respectively. The mean activity ratio of (210)Po/(210)Pb in the urine was 0.73. The mean excretion rates of (210)Po and (210)Pb in faeces were 56.5 and 54.6 mBq d(-1). The mean activity ratio of (210)Po/(210)Pb in faeces was 1.0.