Concentrations of Fe, Al, Mn, Cu, Ni, Co, and Zn were measured in Fucus ceranoides and F. vesiculosus from Pontedeume, a small estuary on the northwest coast of Spain, affected by mining activities upstream and by sewage discharge to the estuary itself. Plants were collected from two intertidal levels at each of six locations, each sample eventually consisting of the homogenized tissues of ten individuals. Tips and thalli were analysed separately. By using these methods, it was found that three or four samples were sufficient to detect differences between means for different sites of 50% for all the metals considered except Cu, the high variability of which made eight samples necessary in order to detect differences of 100%. It was demonstrated that the contribution of particulate matter not removed during washing prior to analysis is significant only in the cases of Fe, Al and Cr. Mn and Co, and, to a less but still considerable extent, Ni and Zn, were found to be greatly enriched in the algae studied. Concentrations in mature tissues were higher than in apices for all the metals studied except Cu, for which there were no significant differences between the two tissues. The vertical position on shore did not affect apical metal concentrations but showed correlations with Mn, Co, Ni, Zn and Cu in mature tissues. Possible reasons for these correlations are discussed.