Abstract. – The concentration of Cd, Cu, Hg, Pb and Zn in the liver of the European eel (Anguilla anguilla) was determined to evaluate the contamination burden of this species in Portuguese brackish water systems (Aveiro lagoon, Óbidos lagoon, Tagus estuary, Santo André lagoon and Mira estuary) and relate it to anthropogenic pressures within those ecosystems. The highest levels of most metals were found in eels from the Tagus estuary, in opposition to specimens from Santo André lagoon, which exhibited the lowest values. These results confirmed that eels from the most impacted areas show higher metal concentrations in their liver. Although little variability in metal load was observed within each brackish water system, some heterogeneity in contamination profiles among sampling stations was detected, demonstrating the efficacy of using the European eel as a sentinel species to monitor metals contamination at both large and small spatial scales.