The biosorption of chromium(VI) and nickel(II) ions, both singly and in combination, by dried activated sludge was investigated in a batch system as a function of initial pH and single- and dual-metal ion concentrations. The working pH value for single chromium(VI) and nickel(II) biosorption was determined as 1.0 and 4.5, respectively, due to the selective uptake of biomass. Multi component biosorption studies were performed at these two initial pH values. It was observed that the biosorption kinetics and equilibrium uptakes of chromium(VI) and nickel(II) ions in binary mixtures changed due to the initial biosorption pH and the presence of the other component.