How macroinvertebrate respond to human disturbances can be characterized following two major approaches. The traditional taxonomic approach has been extensively used. Since the nineties, another approach based on functional traits has experienced and offer a better understanding of community-environment relationships and functioning of ecosystems facing human impacts. In this study, we assessed sediment quality in a large river in North America by exploring the relationships between chemical contamination and benthic community structure using the functional trait approach. This study was carried out in the St-Lawrence River, an essential waterway exposed to many anthropogenic stresses such as industrial and municipal wastewater or agricultural activities. Macroinvertebrates were collected in 59 sites. Organic, inorganic contaminants and sediments characteristics (grain size, organic matter, nutrient, etc) were measured in the whole sediment. Seventeen biological or ecological traits of taxa were coded, taking into account regional climate and ecosystem specificities. The goals of this study were: (1) to describe spatial patterns in functional traits of macroinvertebrate communities; (2) to determine relationships between trait combinations and taxonomic structure and (3) to link macroinvertebrate assemblages and trait combinations to environmental conditions and sediment quality.