In fall 2005, fish contamination by PCBs was observed in the Rhone river in the vicinity of Lyon (France). This incidental observation triggered a series of investigations on fish and sediment all along the main stream, leading to consumption prohibitions along several stretches. In parallel, a project was set up, aiming to develop a model that would describe the transfer of PCBs from sediment to key fish species, in order to help determine sediment management guidelines in the future. Key fishes and invertebrates were caught for PCBs analysis in three sites along the Rhone river: (1) the reference site, upstream Lyon and before the first contaminated area; (2) a site close to Lyon, located in this contaminated area; (3) a site downstream Lyon. The first step of the model's development describes the food webs of these key species, namely the barbel (Barbus barbus), the chub (Squalius cephalus), and two breams (Abramis brama and Blicca bjoerkna), all large and long-living species prone to accumulate PCBs over many years. This description is based on the combined use of analysis of stomach contents in fish, and as well their potential food resources (invertebrates and aquatic plants communities). Moreover, measurements of d13C and d15N isotopes were performed in fish and invertebrates samples, in order to determine their relative position in the food webs. Results of these preliminary investigations will be presented and respective food webs described.