Furfuryl alcohol (FA) in aqueous medium at pH 2.0 and 90°C in presence of H2O2/Fe2polymerized under crosslinking, without grafting to cellulosic fibers if present. Under the same conditions acid-prepolymerized furfuryl alcohol (PFA) transformed into a water-soluble polymer that grafted to cellulosic fibers (polymer load of 68%) with a negligible formation of a crosslinked homo-polymer. Decrease in the reaction temperature or increase in the volume of water decreased the polymer load and grafting efficiency. Increases in the concentrations of H2O2, of Fe2+, of both, or of pH resulted in curves exhibiting maxima in grafting efficiency and polymer load. This was explained by the presence of second and first order members in the equation for the reaction rate of the formation of grafting active centers on PFA or cellulose. Increase in cellulose consistency decreased the polymer load but influenced the grafting efficiency to a secondary extent only, suggesting that activation of PFA rather than that of cellulose is responsible for grafting. Pretreatment of cellulose with H2O2/Fe2+before addition of PFA resulted in no grafting. Pretreatment of PFA before addition of cellulose gave a polymer load amounting to about 401 of what would have been expected if both reaction partners had been reacted simultaneously. This was explained by formation of time-stable active centers on PFA and of time-unstable active centers on PFA or cellulose.