Nylon 6 fibers were metallated with Li, Na, or K methoxide in methanol and the metallated fibers were allowed to graft-copolymerize with various vinyl monomers in tetrahydrofuran (THF), dimethyl sulfoxide (DMSO) or hexamethylphosphoramide (HMPA) by the anionic mechanism. The following results were obtained. (1) In the graft polymerization of various vinyl monomers such as acrylonitril (AN), methacrylonitril (MAN), methyl acrylate (MA), methyl methacrylate (MMA), methyl vinyl ketone (MVK), vinyl acetate (VAc), acrylamide (AAm) and styrene on the metallated nylons in THE and DMSO, AN and MVK were easily polymerized to produce the grafted nylons with high graft yields. MAN, MA and AAm were moderately polymerized to produce the grafted nylons with low graft yields. MMA, VAc and styrene were hardly polymerized. (2) In the graft polymerization of AN on the metallated nylons in various solvents, both the conversions and the graft yields increased with increasing the degree of metallation and the dielectric constant of solvents. The grafting efficiencies were about 100% for the solvents of lower dielectric constant. The number-average molecular weight (_??_n) of the graft chains decreased with increasing the degree of metallation in the range of 900_??_10000. The graft polymerization was depressed by oxygen existed in the reaction atmosphere and consequently the graft yields were in the order of N2>air>O2 atmosphere. Furthermore, the graft polymerization was depressed by additives such as hydroquinone, N-phenyl-β-naphthylamine, water and acetic acid. (3) In the graft polymerization of MMA on the metallated nylons in THF, DMSO and HMPA, the graft polymerization occurred only in HMPA. The graft yields increased with increasing the degree of metallation and in the order of K>Na>Li. The _??_n of the graft chains decreased with increasing the degree of metallation in the range of 400000_??_1100000, The apparent activation energy of the graft polymerization was 13.5 kcal/mol. To confirm the occurrence of graft polymerization, the grafted nylon was alternatively extracted with benzene and 16% CaCl2 solution in methanol (CaCl2/MeOH). Both the CaCl2/MeOH-soluble fractions and the benzene- and CaCl2/MeOH-insoluble fraction were confirmed to be the graft copolymers by IR spectra of each fraction.