Raritan Bay, which is adjacent to the New York metropolitan area, served as a study site to investigate the relationship between copper and lead concentrations in water and in seaweeds. Correlation coefficients of 0.98 for copper and 0.97 for lead indicate a high degree of correspondence between levels of these metals in water and in algal tissue. Concentration factors of 18.4 × 10 4 for copper and 8.2 × 10 4 for lead are among the highest reported to date.