An oxymethylenepolymer is stabilized by incorporation therein of an epoxy compound containing at least two epoxy groups in the molecule and is monomeric unless the polymer is a copolymer containing adjacent carbon atoms when the epoxy compound may also be a resin. Specified epoxy compounds are dicyclopentadiene dioxide vinylcyclohexene dioxide, 3,4 - epoxy - 6 - methylcyclohexyl-methyl - 3,4 - 6 - methyl cyclohexane carboxylate, resorcinol diglycidyl ether and epoxidized drying oils. Phenolic stabilizers may also be present, e.g. diphenylol methane or 2,21-methylene - bis - (4 - methyl - 6 - tertiary butyl phenol). The polymers may be end capped either by esterification or by etherification.