Total arsenic, inorganic arsenic, lead and cadmium contents were determined in 112 samples of seaweed preparations sold in Spain (seaweed packed in plastic or cardboard box, seaweed in the form of tablets and concentrates, foods containing seaweed, and canned seaweed). The concentration ranges found, expressed in mg/kg, dry weight, were: total As (0.031-149), inorganic As (<0.014-117), Pb (<0.050-12.1) and Cd (<0.003-3.55). For all the contaminants there were failures to comply with legislated values. In particular, all the samples of Hizikia fusiforme exceeded the inorganic As limit established in some countries, and a considerable number of species exceeded the Cd limit set by international regulations. With respect to food safety, consumption of 3 g/day of the samples analysed could represent up to 15% of the respective Tolerable Daily Intakes (TDI) established by the WHO. The situation is especially alarming for intake of inorganic As from H. fusiforme, which can be three times the TDI established.