Improvements in physical properties of polyvinyl alcohol fibers were attempted by means of both crosslinking and graft copolymerization. By using the ceric iron redox system on synthetic fibers spun from polymer blends containing polyvinyl alcohol (PVA) and its partially (about 15 mole-%) N-methylolcarbamoylethylated products (PVM) in which the blend ratios were 0/100, 10/90, 15/85, and 20/80 by weight, methyl methacrylate (MMA) was grafted at 30°C. in the aldehyde-free acetone-water system after crosslinking by heat treatment or successive acid treatment. Grafting increases with increasing PVM component. This may be ascribed to the coarsening of the fiber texture caused by polymer blending and the increasing of methylol groups as a reducing agent. Moisture regains decrease with increasing graft fraction, but these appear to be greater than the additive values of backbone and graft polymer. Less shrinkage in boiling water is obtained with the increase of PVM component and grafting; the decreased shrinkage is significant in the acid-treated PVM-PVA fibers, and it reaches a nearly sufficient value at about 50% graft-on. The PVA fibers do not give sufficient shrink-proofing. The inherent tenacity and elongation of the grafted fibers increase slightly with increasing graft-on or denier except at the high grafting above about 100, 150, and 300 in the PVA, acid-treated, and acid-untreated PVM/PVA fibers, respectively; whereas the tensile strength in grams/denier decreases with grafting. Although at high grafting, a destruction in the fiber texture will perhaps occur, the coarser the texture of backbone fiber, the harder the change by grafting. The knot/normal ratios in tensile strength or elongation of the grafted fibers have been retained at above 90%. The elastic recovery of the grafted fibers is considerably improved as compared to the conventional Vinylon fibers. The improvements in the acid-treated and grafted PVM/PVA (20/80) fibers are significantly greater above and below 50% graft-on, especially in the range of lower extension. As expected, the thermosetting property is also appreciably imparted with grafting. In the conventional Vinylon fibers, the formalization for shrink-proofing is usually at a sacrifice of elastic recovery. But MMA grafting in the PVM/PVA fibers gives a fairly good elastic recovery and less shrinkage in addition to thermosetting property, making the most of the characteristics in the longer intermolecular crosslinkages formed between methylol groups or PVA-OH groups and methylol groups.