ABSTRACT: Presented publication describes the developments and the results achieved during the research, exploration and use of ground water in Slovakia since 16th century. Like other fields of science, the hydrogeology also went through a period of intuition and speculation, a period of observations, measurements and experiments and only since 20th century it started to act as an independent field of science. This is also reflected by the topics presented in this publication. While the first two chapters evaluate the degree of knowledge achieved before 50-ties, in other ones, the beginnings and the development of the modern hydrogeology that took place bet ween 1950 and 1999 are described. lndividual chapters were written on the basis of ne w and old data, available in the archival reports and in published papers.