AbstractThe Raritan Bay—Lower New York Bay complex was surveyed to examine xenobiotic—sediment—benthic relationships. The macrofauna, sediment granulometry, extractable hydrocarbons, polychlorinated biphenyls (PCB) and polynuclear aromatic hydrocarbons (PAH) were surveyed concomitantly. PCB and PAH in molluscs and PAH in bottom waters were also measured.A total of 126 species was identified, principally molluscs, polychaetes and crustacea. Mya arenaria, Mercenaria mercenaria, Nereis virens and Glycera dibranchiata were the most abundant. Numerous xenobiotics were detected in the sediments and bivalves at all stations. Correlations of diversity indices, and numbers of bivalve species and polychaete species with specific sediment pollutants were poor or absent. Trends of decreasing diversity and density with increased pollution and/or silt-clay were observed, with more species generally occurring in the lower bay area. The dominant feature determining the distribution and abundance of the fauna appeared to be the sediment characteristics (substrate) and prevailing local currents within areas (zones) of the bay. These factors were further modified by the total hydrocarbon—xenobiotic loading of the sediments.