The abundance of radionuclides in the Arctic Actiniaria has limited study despite their environmental importance in coastal food chains. Although the Arctic has incurred relatively little contamination by anthropogenic radionuclides as a result of nuclear weapons tests, there are still detectable levels of radionuclide activity observed in marine species. In this study of anthropogenic radionuclide activity in Actiniaria from Spitsbergen we observed levels of 90Sr from 0.92 Bq kg-1dw to 18 Bq kg-1dw and for 137Cs from 1.2 Bq kg-1dw to 12 Bq kg-1dw. The highest values of 90Sr and 137Cs were observed in organisms at stations close to seabird colonies and a river mouth, suggesting that fecal material and melting glaciers may be sources of radionuclides in the Arctic environment. The body mass of individual organisms affected bioaccumulation of 90Sr and 137Cs in Actiniaria, with radionuclide bioaccumulation occurring most intensively in the smaller specimens.