The objective of our work is to present the results ol an hydrogeochemical study of springs around the São Paulo Tertiary Basin. In that region they emerge from diaclases, fissures and joints in different types of crystalline rocks. All the analyzed rvaters have similar phvsico-chemical characteristics: temperature close to the annual medium temperature of the air; low conductivity; total salinity under 100 mg/l; acid pH 4.7-5.5; radioactivity 0.7-20.7 nCill. Among the major elements the earth-alcalines are predominant, and the trace elements show variable concentrations. The waters can be classified as magnesian-bicarbonated. On the diagram of Piper, different groups could be separated reflecting the rocks in which the waters circulate. The study of diflerent characteristical relations indicates the relationships between the chemical composition of the waters and the surface lithology, as well as the probable origin of the waters.The objective of our work is to present the results ol an hydrogeochemical study of springs around the São Paulo Tertiary Basin. In that region they emerge from diaclases, fissures and joints in different types of crystalline rocks. All the analyzed rvaters have similar phvsico-chemical characteristics: temperature close to the annual medium temperature of the air; low conductivity; total salinity under 100 mg/l; acid pH 4.7-5.5; radioactivity 0.7-20.7 nCill. Among the major elements the earth-alcalines are predominant, and the trace elements show variable concentrations. The waters can be classified as magnesian-bicarbonated. On the diagram of Piper, different groups could be separated reflecting the rocks in which the waters circulate. The study of diflerent characteristical relations indicates the relationships between the chemical composition of the waters and the surface lithology, as well as the probable origin of the waters.