The geothermal status of Italy's Mt. Etna region was studied via borehole thermometry at eight experimental sites. The mathematical principles and other criteria used in borehole site and well depth selection are discussed. The soil temperature is regulated by external temperature variations to a certain depth. The minimum drilling distance which would provide accurate temperature determinations was calculated to be 30 m. The geothermal gradient was determined by the application of a Fourier series to three measurements made at different depths using resistance thermometers. The results are presented in tables and the gradients are plotted on graphs. Geothermal gradient determinations were corrected for topographic effects. Two major groups of gradients were discovered, those having linear gradients were interpreted as being due to the effect of meteoric waters. Other possible disturbances are those caused by surface temperature effects and the influence of nearby bodies of water.