Extraction of cobalt ions from aqueous medium has been studied, using macroporous polyacrylonitrile-manganese dioxide composite beads. Polyacrylonitrile, synthesized by gamma-radiation induced polymerization of saturated aqueous solution of acrylonitrile monomer, has been employed, to produce polyacrylonitrile-manganese dioxide composite beads. Results of the extraction study indicate efficient adsorption of cobalt ions from neutral, or slightly acidic, aqueous solutions. The cobalt ions, adsorbed on the composite beads, can be leached out with 0.1M HNO3 solution. The effect of various experimental parameters, such as concentration of cobalt ions, pH of the aqueous solution, etc., on the adsorption process and its kinetics has been studied. Further, adsorption capacity of the beads for cobalt ion, as well as their reusability for multiple adsorption-desorption of the cobalt ions, have also been evaluated. SEM and BET techniques have been used to determine the porous nature of the beads. IR spectroscopy has been used to understand the interaction of the polyacrylonitrile-manganese dioxide composite beads with cobalt ions.