In certain areas of the French Atlantic coast, algae of marine origin are used as organic fenilizer, particularly for vegetables cultivation. An experiment was carried out to estimate the transfers of radioactivity towards agricultural productions, which could result from this practice in the case where algae were contaminated Algae (fucus vesiculosus) were cultivated in aquarium with seawater containing a mixture of radionuclides: "Na, *°Co, w Sr, "TC, l06 Ru, l2i Sb, IM ' ll7 Cs, 238 - I№,2w Pu i 1,1 Am, 2**Cm. These algae were mixed, in a lysimeter, with a silty- sandy soil. Some vegetables, potatoes, lettuces, radishes, beans, tomatoes were cultivated on this manured soil. The soil to plant concentration ratios are given for the edible organs of the plants grown the year following the addition of algae in the soil and for cultures made several years later. On the other hand chemical extractions were performed to evaluate the bioavailable fraction of radionuclides in the soil.