In this paper copper biosorption on a specially propagated biomass of Rhizopus oligosporus has been studied considering kinetic and equilibrium aspects. A rough biomass characterization performed by titration tests suggested that over pH 3-4 all biomass active sites seem available for metal adsorption. A maximum copper-specific uptake of about 140 mg/g was observed at pH 5. Kinetic tests evidenced that the process is very fast: in fact, biosorption equilibrium is reached within the first 20 min. Furtermore, kinetic data were successfully modeled by second-order models. Equilibrium data were obtained by pH-edge tests, and copper uptake was modeled considering the pH and equilibrium concentration in solution as independent variables: different empirical and semiempirical models have been proposed to model biosorption equilibrium and successfully fitted to experimental data.