Amphipods are considered a sensitive group to pollution but here different levels of sensitivity were detected among species, by analysing the impact of five sewage outfalls, with different flow and treatment levels, on amphipod assemblages from the Castellon coast (NE Spain). Sewage pollution produced a decrease in the abundance and richness of amphipods close to the outfalls. Most of the species showed high sensitivity, particularly species such as Bathyporeia borgi, Perioculodes longimanus and Autonoe spiniventris, whereas other species appeared to be more tolerant to the sewage input, such as Ampelisca brevicornis. These different responses could be related to burrowing behaviour, with fossorial species being more sensitive and domicolous species being less affected. Benthic amphipods, which live in direct contact with sediment, are widely used for bioassay and numerous species are usually employed in ecotoxicology tests for diverse contaminants. In order to consider amphipods for monitoring and biodiversity programmes, it is important to establish the degree of sensitivity of each species to different sources of pollution.