Beside uranium and radium, arsenic is one of the most important contaminants in seepage water from former uranium mining and milling sites. As several bacterial isolates from these sites and some reference strains are known to bind large amounts of toxic metals, arsenic binding capacity of their cells and S-layers were investigated and compared to that of granulated ferric hydroxide (Ferrosorp). Surprisingly, some S-layers possess a 2 to 5-fold higher binding capacity in comparison to the Ferrosorp material.