A biofilm of Arthrobacter viscosus, supported on granular activated carbon, removed between 100% and 50% of Cr(VI) and between 100% and 20% of Cd(II) from solutions with initial concentrations between 4-11 mg(metal) l(-1) and a flow residence time of 1.2 min. For experiments of lower initial concentrations, a steady-state removal of 50% was reached after 71 bed volumes of Cr solution passed through the biosorbent bed and a steady-state removal of 30% was reached after 47 bed volumes of Cd solution passed through a similar bed. Final uptakes of 8.5 mg(C)r g(carbon)(-1) and 4.2 mg(c)d g(carbon)(-1) were determined for initial concentrations of 10 mg(Cr) l(-1) and 11 mg(Cd) l(-1), respectively. The influence on the overall process of two different surface treatments of the support was evaluated and compared with the behavior of a support not treated.