Graft copolymerization of 2-hydroxyethyl methacrylate onto polypropylene monofilament was carried out by using a simultaneous gamma radiation technique from a60Co source, so that the hydrogel polypropylene-g-polyhydroxyethyl methacrylate thus produced by grafting could be used as a biocompatible suture material. the influence of various parameters, such as dose rate, total dose, and monomer concentration, on the degree of grafting was determined. It was found that the degree of grafting increases with an increase in monomer concentration. However, for a constant dose under optimum monomer concentration (1.5–2.0 mol/L), a low dose rate produces better graft levels. the studies showed that grafting is strongly influenced by the reaction medium. the optimum conditions for the system were determined. the grafting was ascertained by infrared spectroscopy and color formation with methylene blue. the grafted monofilament showed very good swelling behavior in water due to the incorporation of hydrophilicity in the copolymer monofilament.