Summary: The grafting of styrene into commercially available fluoropolymer films by the pre-irradiation method has been investigated. Poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA) and poly(tetrafluorethylene-co-ethylene) (ETFE) were chosen as the base polymer material. The influence of the base material, the pre-irradiation dose, and the storage time between the irradiation and the grafting step on the yield of grafting was examined. The base materials were pre-treated by irradiation in the molten state under oxygen-free conditions in order to create branches and cross-links. The effect of pre-treatment on the yield of grafting was studied.