The occasion offered by the Symposium on the History of Geothermal Energy, held at Mexico City in January 1992 in the framework of the Third Latin American Congress on the History of Science and Technology, gave the cue to this writer and to several Italian and Mexican colleagues to begin an investigation into the relationships that man had with geothermal energy in some regions of the world prior to the Modern Age. This investigation has the aim not only of gaining greater insight into the ancient uses of natural heat and its by-products; but, also extends to gathering elements for comprehending what kind of "impact" the presence of geothermal manifestations, and the occurrence of volcanic eruptions may have produced on the ancient inhabitants of those regions