This article describes the graft copolymerization of poly(methyl methacrylate) (PMMA) onto oil-palm empty fruit bunches (OPEFBS) with a fiber length of less than 75 mu m. The graft copolymerization was carried out under a nitrogen atmosphere by a free-radical initiation technique in an aqueous medium. Hydrogen peroxide and ferrous ions were used as a redox initiator/ cocatalyst system. The PMMA homopolymer that formed during the reaction was removed from the grafted copolymers by Soxhlet extraction. Determining the effects of the reaction period, reaction temperature, and monomer concentration on the grafting percentage was the main objective, and they were investigated systematically. The optimum reaction period, reaction temperature, monomer concentration, and initiator concentration were 60 min, 50 C, 47.15 x 10(3) mol, and 3.92 x 10(3) mol, respectively. The maximum percentage of grafting achieved under therse optimum conditions was 173%. The presence of PMMA functional groups on OPEFB and the enormous reducion of the hydroxyl-group absorption band in PMMA-g-OPEFB spectra provided evidence of the successful grafting reaction. The improvement of the thermal stability of PMMA-g-OPEFB also showed the optimal achievement of the grafting reaction of PMMA onto OPEFB. (c) 2008 Wiley Periodicals, Inc.