ABSTRACT Trace elements in aquatic ecosystems are considered as major pollutants due to their environmental persistence, toxicity and ability to be incorporated into food webs.  Contaminated sediments represent a threat to benthic macroinvertebrates which in turn expose high trophic organisms to hazardous trace elements, therefore metals accumulated in benthic organisms can also be bio concentrated in food webs. Direct toxic effects of metals include changes in diversity and abundance of benthic invertebrates while, indirect effects include modifications of species interactions and reductions in food quality. In this work, we study the potentially toxic metal concentrations in both sediments and benthic macroinvertebrates in the Maipo River basin (central Chile) evaluating the risk assessment of sediment, toxicity to the biota and bioaccumulation in the organisms.  Sediments and benthic organisms were sampled in spring (October-December) 2016 from four sites of the Maipo River basin. Twelve trace elements (As, Al, Cd, Cu, Cr, Hg, Fe, Mn, Mo, Ni, Pb and Zn) were determined by AAE. The Geo accumulation index showed that Zn was moderate to strong pollute in all sites and the enrichment factor showed that there were no important anthropic impacts in the river. High level of contamination was found for Cu in PEL and the pollution index showed that PEL was extremely polluted. Three (Cu, Mn and Zn) out of the five metals analyzed were the elements which presented the largest toxicity to organisms in these aquatic systems based on the Threshold Effect Concentration (TEC) and Probable Effect Concentration (PEC) analysis. Most of the metals analyzed did not show bioaccumulation; however, Ni and Pb were the metals with the highest bioaccumulation factor in all the studied sites. Key words: sediments, benthic organism, Enrichment Factor, Geo accumulation index, sediments toxicity TEC and PEC, bioaccumulation, Trace elements, EAA