This work presents new results on the arsenic distribution in the groundwater from the SW of Uruguay.This preliminary study is based in 28 samples from the Aquifer Systems Chuy, Raigón and Mercedes. Thearsenic concentrations observed exceed some thresholds of the Uruguayan and other (e.g., WHO)regulations of water quality. The median, maximum and minimum determined have been 16.9, 58.0 and0.1 µg/l, respectively). There is a horizontal and vertical variation of the concentrations considering alltogether the studied aquifers and also within them. The higher values have been observed in the MercedesAquifer in areas near the Uruguay Rive
