[en] As part of the national survey to evaluate natural radioactivity in the environment, concentration levels of natural uranium and ²²⁶Ra have been analyzed in over 300 drinking water samples taken from different locations in Argentina. ²²⁶Ra was determined by ²²²Rn emanation and liquid scintillation counting, and natural uranium by a fluorimetric procedure. Values ranging from 0.03 to 24 μg.l^-1 of natural uranium and from 0.06 to 50 μg.l^-1, were measured on drinking water samples taken from tap water systems and private wells, respectively. Concentrations up to 15 mBq.l^-1 and to 22 mBq.l^-1 of ²²⁶Ra were found in drinking water samples taken from tap water systems and private wells, respectively. These values are compared with the reference values accepted for drinking water. Based on the water intake rate, the age distribution and the measured concentrations, an annual collective effective dose of 1.9 man Sv and an individual committed effective dose of 0.49 μSv.y^-1 were calculated for the city of Buenos Aires adult inhabitants, for the ingestion of both natural radionuclides analyzed in drinking water. (author)