[en] In a preliminary study, in vivo skull measurements and in vitro urine measurements of ²¹⁰Pb and ^natU have been performed to find out the individual, chronic exposure to waterborne natural radionuclides of a small group of Finnish people. For their domestic water, the studied individuals use water from drilled wells containing elevated concentrations of natural uranium and its daughter nuclides (^234,235,238U, ²²²Rn, ^226,228Ra, ²¹⁰Po,²¹⁰Pb). Enhanced ²¹⁰Pb and ²³⁵U activities were observed in several persons. A positive correlation is observed between the U concentration in urine (μg d^-1) and the number of counts (cpm) in the gamma ray energy peaks originating from the decay of ²³⁵U and ²³⁴Th respectively. Calibration of the detector set-up and the determination of background sources are in progress. (author)