Chemical and H- and O- isotopic compositions of 13 hot spring waters in the eastern part of Toyama Prefecture were analyzed to examine their chemical characteristics and to estimate the underground temperature for new geothermal exploration. On the basis of chemical and isotopic compositions, the hot spring waters can be divided into two groups: low and high salinities. The low salinity group is of meteoric origin and high one is a mixture of seawater and meteoric water with an oxygen isotopic shift. The latter may be geo-pressured fluid, which is characterized by high delta D values of approximately -20 parts per thousand and medium Cl concentrations of approximately 6,000 mg/L, as reported elsewhere. The results of estimated underground temperatures support the view that the area along the Kurobe River has one of the highest geothermal potentials among the studied fields. (C) 2013 The Authors. Published by Elsevier B. V. Selection and/or peer-review under responsibility of the Organizing and Scientific Committee of WRI 14-2013