Sampling of benthic communities from the Catalonia rocky littoral (NW Mediterranean) was carried out in 1999-2000 to study the environmental quality of the waters, using the organisms as bioindicators, and DCA analysis as ordination method. Coverage of the main organisms was used as descriptors of the ecological state. Cystoseira mediterranea was the dominant species in the north coast, whilst the central and south coasts were mainly dominated by Corallina elongata and Mytilus galloprovincialis. Samples in reference zones (non-polluted areas, with almost nil human influence) were also introduced in the analysis to compare the water quality of the different stations in the Catalan coast with these of “pristine” areas. Our results are compared with previous data obtained in 1982. We observe changes in the structure of the littoral communities since 1982, with an apparent increase of the environmental quality. There is a decrease in the abundance of green-algae but we do not observe an increase in the abundance of Cystoseira. These changes can be related to the implementation of the management of the residual waters since 80’s years.This study has been financed by the Water Catalan Agency (ACA) of the Environmental Department of the Generalitat of Catalonia.Peer reviewed