Uranium and polonium isotopes were measured in tap water and groundwater from the Warsaw area (Poland). The mean values of 210 Po, 234 U and 238 U in surface intakes were 0.12, 3.91 and 2.75 mBq dm −3 and for deep water intakes were 0.25, 0.24 and 0.20 mBq dm −3 , respectively. The annual dose absorbed as a result of the consumption of drinking water by a inhabitant was calculated on the basis of measurements of polonium and uranium activity. The calculated value is only a negligible part (approximately 0.02%) of the dose taken from natural sources, which is estimated at 2.4 mSv year −1 .