Concentrations of mercury were determined for tinned molluscs (Mollusca, Bivalvia), i.e., mussels (Mytilus spp.), cockles (Cerastoderma edule), variegated scallops (Chlamys varia), and razor shells (Ensis spp.), consumed in Spain. A total of 220 samples were analyzed: 120 mussels, 40 cockles, 24 variegated scallops, and 36 razor shells. Samples were obtained weekly from markets in Santa Cruz de Tenerife (Canary Islands) over a period of 12 months. All observed concentrations of mercury were below the maximum permitted for human consumption (0.5 mg/kg) as defined by European Community Decision 93/ 351/CE. Mercury concentrations were 27.28 +/- 12.43 microg/kg for mussels, 66.59 +/- 23.53 microg/kg for cockles, 33.68 +/- 15.76 microg/kg for variegated scallops, and 21.26 +/- 12.24 microg/kg for razor shells. To evaluate the importance of mercury as a food contaminant, the percentage ingested daily, the weight of mercury in the diet, and the calculated percentage of this metal in the diet contributed by reference species were estimated.