Polonium-210 has been analysed in the soft part of two bivalves species, the scallop Chlamys varia and the common mussel Mytilus edulis, from the bay of La Rochelle and Ré Island, on the french Atlantic coast. Between those sites, the highest 210Po concentrations have been found in whole scallop soft parts from La Rochelle, reaching 1181+/- 29 Bq/Kg-1 dry weight (dwt), a size effect being related to the highest 210Po concentration in the smallest scallops. The results show a significant difference in concentrations for similar size individuals between species in each site(C. varia > M. edulis) and between sites for each species (Ré island > Bay of La Rochelle). very high 210Po concentrations have been found in the digestive gland of C. varia, ranging 3150-4637 Bq/Kg-1 dry weight (dwt). Thus, the digestive gland contains up to 60% of the radionuclide. Subcellular investigations have shown that approximately 40% of tht 210Po contained in the digestive galnd is in the cytosolic fraction, suggesting a high bioavailability of the 210Po from this fraction to the trophic upper level. Calculations will show that approximately 4Kg of scallops flesh intake would be necessary to reach the annual incorporation limit of 1mS.