In this work the potential of Catla catla scales to remove Cr(VI) ions from aqueous solutions was investigated as a function of time, initial Cr(VI) concentration, initial pH, biomass dose and agitation speed. Optimum biosorption conditions were found to be pH 1.0, 0.05 g L-1 biomass dosage, 200 rpm agitation speed and 180 min equilibrium time. The fitness of biosorption equilibrium data for Freundlich, Langmuir and Dubinin-Radushkevich isotherm models were tested. It was found that Freundlich model was better suitable for biosorption of Cr(VI) ions onto C. catla biomass. Three kinetic models viz. the Lagergren firstorder and pseudo-second-order and intra-particle diffusion model were used to analyze the biosorption data and the results suggested that the pseudo-second-order model represented the best correlation. FTIR spectrum analysis revealed that O-H, N-H and C-O groups were the leading Cr(VI) binding groups. (C) 2009 Elsevier B. V. All rights reserved.