The graft copolymerization of acrylic acid (AA) and 2-acrylamido 2-methylpropane sulfonic acid (AASO(3)H) onto cellulose, in the presence or absence of crosslinking agent N,N'-methylene bisacrylamide (NMBA), by using different concentrations of eerie ammonium nitrate (CAN) initiator in aqueous nitric acid solution at either 5 or 30 degreesC was investigated. To investigate the effect of pretreatment of cellulose on the copolymerization, before some grafting reactions cellulose was pretreated with either 2 or 20 wt % NaOH solutions or heated in distilled water/aqueous nitric acid (2.5 x 10(-3) M) at 55 degreesC. To determine how the excess of initiator affects the grafting and homopolymerization, separate reactions were carried out by removing the excess of eerie ions by filtration of the mixture of initiator solution and cellulose before the monomer addition. Extraction-purified products were characterized by grafting percentage and equilibrium swelling capacity. Pretreatment of cellulose with NaOH solutions decreased the grafting percentage of copolymers. In the case of AA-AASO(3)H mixtures, nonpretreated cellulose gave a higher grafting percentage than NaOH-pretreated cellulose. Filtration also lowered the grafting of AA on the cellulose in the cases of pretreatment with either water or nitric acid. Copolymers with the highest grafting percentage (64.8%) and equilibrium swelling value (105 g H2O/g copolymer) were obtained in grafting reactions carried out in the presence of NMBA at 5 degreesC.