Description: Polycyclic aromatic hydrocarbons (PAHs) are key contaminants of concern under the Arctic Environmental Monitoring Programme (AMAP) due to their carcinogenic potential. The concentration of the different PAH components may be connected to the geochemical background of the sediments, including leakage and erosion of fossil carbon, as well as epigenetic processes such as decaying peat. In other cases there is a human influence connected to petroleum spills or combustion of fossil fuel or other human activities. The overall goal of this study was to identify and analyze existing comparable datasets on PAHs from Norwegian and Russian arctic shelves, and use the concentration and composition of PAH components in the selected datasets to assess baseline concentration of PAH, geographical anomalies and sources and routes of transport, as well as the human impact. PAHs in 330 samples of surface sediment from the Barents and Kara Sea shelves, collected during the period 1991-1998, have been selected for the study. In the Southwest Barents Sea the nature of PAHs is formed by a complex sedimentation regime made up of inflowing Atlantic and North Sea water, coastal discharges, coastal abrasion and atmospheric transport. The PAHs basically correspond to background compositions with a low but notable anthropogenic influence. In the Northern Barents Sea both concentration and composition of PAHs are genetically (genesis, conditions and level of transformation) connected with eroded sediment material from the Spitsbergen and Franz Josef Land archipelagos. The relative high PAH levels observed off Spitsbergen thus generally may have a non- anthropogenic explanation. In the central part of the Barents Sea the PAH levels in the deep-water bottom sediments are generally low, non-anthropogenic in origin, and determined by endogenous processes. Erosion and re-deposition of Novaya Zemlya strata do not have a significant influence on PAH composition in this part of the Barents Sea. In the Southeast Barents Sea (Pechora Sea) the PAH composition corresponds, in general, well with the PAH allocation in the Barents Sea. However, the terrigenous influence is stronger. The PAH composition exhibits both epigenetic processes (such as the high level of perylene which most probably is derived from decaying peat) and the presence of petrogenic PAH. The latter findings may be due to the influx of rivers draining oil-rich onshore territories. In estuaries and offshore the Kara Sea the PAH composition of bottom sediments reflects the significant influence of river run-off (with the same patterns as in the Pechora Sea), but also atmospheric transport of combustion derived PAHs, most probably from the smelters in Norilsk.