Composite collections of channel catfish (Ictalurus punctatus), white perch (Morone americana), their prey items (forage fish and epibenthos), and surficial sediment were collected in the Delaware River estuary in Fall 2001 and Spring 2002 to quantify polychlorinated biphenyl (PCB) accumulation and to examine the mechanisms of bioaccumulation and trophic transfer. Samples were collected from four zones in a section of the Delaware River from Trenton, NJ to Liston Point, DE, and analyzed for lipid content and the hydrophobic organic contaminants PCBs. Our results indicate PCB levels and congener distributions in biota reflect spatial and temporal trends in ambient PCB concentrations. PCB congener patterns vary among sampling zones, with higher homologue groups enriched in lower zones. Demersal species have similar congener accumulation patterns. The presence of highly chlorinated congeners in lower zones does not reflect commercial Aroclor mixtures, indicating a possible point source of PCB contamination in the region downstream of Philadelphia, Pennsylvania. The relationships between total PCB levels in biota and those in water and sediment was constant over the study area based on bioaccumulation parameters. Ambient water quality criteria calculated for the Delaware River with estuarine-specific values derived from this study indicates a major reduction in PCB point and non-point loadings is necessary to reduce PCB contamination in fish, thereby meeting acceptable risk levels for human consumption.