Radiological assessment of bottled mineral waters and thermal spring waters collected from various natural sources in Turkey was carried out using gross alpha and gross beta counting techniques. For 40 samples of bottled mineral water, the mean gross alpha activity concentration was determined to be 164 mBq l(-1) (min.:7 mBq l(-1); max.: 3042 mBq l(-1)), whereas the gross beta activity concentration was found to be 555 mBq l(-1) (min.: 21 mBq l(-1); max.: 4845 mBq l(-1)). For 24 samples of thermal spring water, the mean gross alpha activity concentration was obtained to be 663 mBq l(-1) (min.: 18 mBq l(-1); max.: 3070 mBq l(-1)). The gross beta activity concentration for these samples, on the other hand, was determined to be 3314 mBq l(-1) (min.: 79 mBq l(-1); max.: 17955 mBq l(-1)). These values lead to the average annual effective doses of 313 µSv for mineral waters and 1805 µSv for thermal spa waters, which are found to be higher than those recommended for drinking waters by the World Health Organization. It should be noted, however, that one will get less dose from mineral waters since the daily consumption is much lower than 2 l that these calculations assume.