A series of cation exchange resins were prepared from some low-value agricultural residues. Carboxylate (maleate, succinate, end phthalate), phosphate, and sulfate groups were incorporated onto the complex polysaccharide matrix of oat hulls, corn cobs, and sugar beet pulp. Standard reaction conditions were established, using cellulose as the model polysaccharide. The magnitude of functional group incorporation, under standard conditions, was taken as a measure of the reactivity of the agricultural residues studied. In general, the order of reactivity was sugar beet pulp > corn cob > oat hull. The unsubstituted and the functionalized agricultural residues were tested for their potential ability to remove cations from waste water discharges. The capability of these materials to remove cations from waste waters was estimated from their calcium binding capacity. The calcium binding capacities of the resins prepared from the agricultural residues varied from around 559-3466 mu equiv/g.