The structure of the macrobenthic community, sediment toxicity, and sediment contamination changed greatly between 1980 and 1983 along a pollution gradient from the Los Angeles County Sanitation Districts' (LACSD) sewage outfalls on the Palos Verdes Shelf, California, USA to a reference site in northern Santa Monica Bay. Stimulation of the species richness, biomass, and density of the benthos along the 60 m contour 5 to 11 km from the outfalls was significantly reduced in 1983 when compared to 1980. Stations 1 to 3 km from the outfalls in 1980 were occupied by a depauperate fauna strongly dominated by the opportunistic polychaete Capitella spp. In 1983 species richness and biomass significantly increased close to the outfalls, and Capitella spp. was much less abundant. There was no significant toxicity associated with any sediment from the Shelf in 1983.