One of the sources of exposure to natural radioactivity for humans is natural water. ²²⁶Ra is a natural radionuclide, an alpha emitter which level is continuously monitored in water because of toxicological effect of alpha rays on organism which is a by-product of ²²⁶Ra decay. Following oral administration via drinking water, the toxicokinetics of ²²⁶Ra is similar to the calcium pathway in the body and it could be deposited into the bone. Being an α particles-emitting radionuclide, the 226Ra irradiates bone surface-lining cells and has resulted in an excess incidence of carcinoma, in particular osteogenic sarcomas. Activity concentration of ²²⁶Ra is determined in samples of tap water, water from cisterns, rivers, mineral and thermal water. ²²⁶Ra is radio-chemically separated from water by precipitation using BaSO₄ and the activity is measured by alpha counting. Activity concentrations of ²²⁶Ra in different samples ranged from 3 Bq mˉ³ in water from cistern to 8990 Bq mˉ³ in thermal water. For different types of natural water, taking into account the different uptakes, total effective doses were assessed and the results were in compliance with national regulations (0.1 mSv yˉ¹). For samples of tap water, water from cisterns, rivers and mineral waters effective dose was in the range 0.32 - 90.94 μSv yˉ¹, whereas for thermal waters it ranged from 0.81 - 70.48 μSv for a period of 4 weeks.