A preliminary geochemical sampling survey carried out on the continental shelf along the Côte d'Azur has enabled us to delineate a certain number of areas contaminated by mercury. In the superficial marine sediments of this zone, the highest mercury contents (harbours excluded) were found in the following areas : the Bay of Villefranche with Hg content up to 1.500 microg/kg (1.500 ppb), the Bay of Cannes with an average of 700 microg/kg and also, to a lesser extent, in the Bay of Nice with values reaching 550 microg/kg. In harbours such as Villefranche and Cannes, the Hg content of the sediment reaches 13.000 microg/kg (13.000 ppb). Thus the highest concentrations are mainly localized in waters where yachts and other boats are often brought to anchor. The reported concentration figures refer to the sieve fraction inferior to 0,063 mm; the values we obtained in using the whole sediment are practically the same : the Hg content of the coarser fraction (superior to 63 microns) generally lies in the same range as that encountered in the finer fraction.