This work revealed that although the concentrations of metals in Ebro River water were generally low or even undetectable, in sediments could reach values of concern, especially for Hg, As, Cr, Zn, Ni and Cu. This proved the necessity of taking into account more seriously levels of trace elements in sediments. The BCR method allowed studying how metals are associated with the solid fraction of the sediment, as well as allowed the prediction of the bioavailable fraction and the distinction between geological and anthropic pollution. Bioaccumula- tion results indicated that undetectable concentrations of metals in water are not guarantee that these will not be accumulated in fish in high concentrations, as it has been observed and predicted by means of BCR for Hg, Cd and Cr. Regarding to biological indices, diatoms has been the most sensitive community to metal pollution, followed by macroinvertebates and macrophytes due to metal pollution. However, as it has been stated in this work, the complexity of aquatic systems and the high quantity of variables that could influence in the pollutants toxicity sometimes makes difficult to found answers for all observations and it has been demonstrated that further researchto develop biological indices with more specificity and sensitivity towardsmetal pollution are still needed.