ABSTRACT: The history of mineral waters hydrogeology in Sliač started to be written in the year 1867 and follows during the years 1899, 1921, 1931, 1936, 1939, 1949 and 1959. The research of these waters is still continuing from the 1959 year up today. The last works were finished in the year 1995. The opinions about their deep tectonical origin lasted to the end of the year 1930. From the beginning of 1931 year are accepted the opinions about their infiltration origin, genesis and chemistry in rock environment and about the neovulcanic origin of CO2.