U is found in ground and surface waters due to its natural occurrence. In some cases, its presence is due to human activities such as mining and milling U. It is also found in drinking water. The range of concentrations existing in drinking water supplies in the USA was tabulated and examined. The range of isotopic abundances were also listed. Projections from the available data led to estimates that of the 59,812 community drinking water supplies in the USA, 25-650 exceeded a U concentration of 20 pCi/l, 100-2000 exceeded 10 pCi/l and 2500-5000 exceeded 5pCi/l.