An alternative for supplying water to industry and population has been the utilization of groundwaters. In the Piracicaba region, where the sources of surface waters show the highest pollunt contents in Brasil, the utilization of ground waters has been tried. As a contribution to the practical steps in the establishment of a series of artesian wells, a systematic study has been initiated on the quality of these waters, with a view to its utilization as water supply for the population, industry and agriculture. For this study, samples of groundwater of the Piracicaba region were analyzed from 20 artesian wells, 4 artesian flowing wells, 5 phreatic wells and 3 springs. Determination of D and (18)0 isotope concentration were made using mass espectrometry and the correlation of these data with the D and (18)0 concentration previously determined by SALATI et alii (1974) for the rainwater in the same region and for the Piracicaba river has been studied. Chemical analyses also were made. These preliminary analyses suggest that: a) due to the small variations observed in the isotopic concentrations, the groundwater obtained from the various wells in the region may be representative of a single aquifer; b) the equivalence between the D and (18)0 concentration in the groundwater suggest rather permeable recharge zones; c) the higher isotopic concentrations in the water of the Piracicaba river when compared of the groundwater concentrations indicate that this river is a drainer of the aquifers in the region under study; d) generally speaking, the groundwaters showed to be inadequate for human consumption; e) evidence has also been found that most of the deep wells have a small outflow. In addition, this study has made available further information which will be of great help in future hydrogeological studies.