ABSTRACT. – A survey was carried out both inside and outside the Ancona Harbour (northern Adriatic Sea) in May 2009 to study the effects of some stressors on macrozoobenthos. Relevant organic enrichment and significantly high heavy metal and PAHs content characterized the internal muddy sediments, whereas sand dominated outside. Higher values of density were recorded outside the port, while no differences were observed in terms of species richness and diversity. Sand and zinc together explained almost 51 % of the variation in the species data. Sand-bottom species dominated the external sites. Most of these species are sensitive to the contaminants and their absence inside the port was likely related to the contaminant contents. Inside the harbour most of the species were positive indicators of pollution. Overall results indicated that chemical features seem to be more important than physical composition of the seabed on species distribution.