Résumé : The concentrations of Zn, Pb, Cd, Fe, Cr, Cu, and Ti were measured in specimens of the echinoid Paracentrotus lividus from three Posidonia oceanica meadows in the NW Mediterranean (Marseille, France; Ischia, Italy; Calvi, Corsica). Investigated metals were selectively distributed among the echinoid body compartments (i.e. body wall, Aristotle's lantern, digestive wall, and gonads); their concentrations were influenced by season. The present work emphasises the need to consider both body compartment and sampling period as important factors in studies intending to use P. lividus as a biomonitor species. In particular, digestive wall and, secondarily, body wall and gonads are recommended for use in biomonitoring programmes, though with some restrictions for gonads. Concentrations of most metals differed significantly in the echinoid body compartments according to the seagrass meadow considered. However, these differences were generally of low amplitude, except for Fe and Ti (contaminations by these two metals showed significant departures from background concentrations in echinoids from Ischia). Results suggest that the meadows of Calvi and Marseille, although subject to different pollution status (the meadow of Calvi is considered as a reference meadow while the Marseille meadow is exposed to intense domestic and industrial discharges), showed similar patterns of metal contamination.