Graft copolymerization of methyl methacrylate onto mercapto-chitin has been examined. The copolymerization reaction proceeded efficiently in dimethyl sulfoxide at 80 degrees C to give chitin-graft-poly(methyl methacrylate)s. The grafting percentage increased with the amount of the monomer and reached above 1200% under appropriate conditions. The resulting graft copolymers exhibited remarkable affinity for various common organic solvents.