Neutron activation study of elementary composition was performed on edible sea urchins Paracentrotus lividus from the National Park of Port-Cros. The analysis allows the identification and quantification of 22 elements: antimony, arsenic, baryum, bromine, cerium, chromium, cesium, cobalt, gold, iron, lanthane, potassium, sodium, rubidium, samarium, scandium, selenium, silver, strontium, thorium, uranium and zinc. The concentration levels were higher in the soft organic parts (alimentary canals and gonads) for all the elements, except for strontium, which developed a strong affinity with calcareous hard parts (tests, spines, masticating apparatus). We also found high rates of baryum, arsenic, zinc, bromine and iron. The hypothesis on the origin of these elements is discussed. The data obtained on this referential zone will soon be used to appreciate the perturbation of the elementary composition of urchins by pollution in various parts of the French seashore.