Oscillatoria anguistissima showed a very high capacity for Zn2+ biosorption (641 mg g(-1) dry biomass at a residual concentration of 129.2 ppm) from solution and was comparable to the commercial ion-exchange resin IRA-400C. Zn2+ biosorption was rapid, pH dependent and temperature independent phenomenon. Zn2+ adsorption followed both Langmuir and Freundlich models. The specific uptake (mg g(-1) dry biomass) of metal decreased with increase in biomass concentration. Pretreatment of biomass did not significantly affect the biosorption capacity of O. anguistissima. The biosorption of zinc by O. anguistissima was an ion-exchange phenomenon as a large concentration of magnesium ions were released during zinc adsorption. The zinc bound to the biomass could be effectively stripped using EDTA (10 mM) and the biomass was effectively used for multiple sorption-desorption cycles with in-between charging of the biomass with tap water washings. The native biomass could also efficiently remove zinc from effluents obtained from Indian mining industries.