PURPOSE: A polymer composition capable of being crosslinked by irradiation with accelerated electron beams or ultraviolet rays, prepared by adding a functional monomer to a 4-methylpentene-1 polymer.

CONSTITUTION: The titled polymer composition capable of being cured by irradiation with accelerated electron beams or ultraviolet rays, comprising a 4- methylpentene-1 polymer (a homopolymer or a copolymer with below 40wt% propylene, styrene or the like) and a crosslinking-accelerating functional monomer (e.g., trimethylolpropane trimethacrylate, or triallyl isocyanurate), wherein the amount of said functional monomer is 0.1W15pts.wt. per 100pts.wt. polymer. Although the 4-methylpentene-1 polymer does not undergo crosslinking when it is irradiated with electron beams, it is rendered crosslinkable by the addition of a small amount of the functional monomer.