RESUMEN
Studies were carried out to investigate the contamination of Piracicaba and Mogi-Guaçu River basins (Säo Paulo State, Southeastern, Brazil) for heavy metals (Cd and Pb), using the limnic bivalve Anodontites trapesialis as a biological monitor. The results showed that the concentrations of Pb were higher than the control group in both basins, showing the bioavailability of this non-essential element in the basins. The concentrations were higher in the Mogi-Guaçu than in the Piracicaba basin, and in the slightly contaminated sites in both basins. There was no correlation between the degree of human impact and Cd and Pb concentrations, it was not possible to infer about concentrations of these heavy metals in the bivalves based only in a broad evaluation of human impact