Hexavalent chromium biosorption from aqueous solutions by dried biomass, immobilized dried and immobilized live Synechocystis sp. but also plain Ca-alginate beads was studied. Maximum biosorption capacities of dried biomass, immobilized dried, immobilized live cyanobacterial forms and plain Ca-alginate beads were found to be 78.20, 6.67, 5.38 and 3.58 mg/g, respectively (pH 2.0, 25 degrees C, 60 min). Langmuir and Freundlich isotherm models were suitable for describing the biosorption of chromium by dried biomass of Synechocystis sp. All the tested cyanobacterial forms were regenerated using 0.1 M HCl with up to 90% recovery; and biosorbents were reused in 5 biosorption-desorption cycles without any considerable loss in sorption capacity.