In fall 2005, fish contamination by PCBs above the threshold for fish consumption was observed in the Rhone river, in the vicinity of Lyon (France). This incidental observation triggered a series of investigations on fish and sediments contamination all along the main stream, and is currently extending to tributaries. The data gathered during this still ongoing process should help managers to identify the main sources among the host of potential ones, provided distinct patterns can be identified in relation to these sources. PCB congener pattern analysis in sediments is challenging because weathering processes will modify the original patterns in several ways; moreover, at mid- or downstream sites the various upstream sources will provide mixed patterns. Classical multivariate analyses suffer several pitfalls for such pattern analysis, making it difficult to clearly discriminate among PCB sources. A combination of information about sources or weathering processes, and classification approaches, should nevertheless help to establish relationships between the patterns observed in sediment layers and the sources, yielding an approach helping to sort out priorities for further diagnosis or management actions. The method's development and the first results obtained will be presented.