Electron beam irradiation is known for crosslinking effects in polymers. Respective treatment is used worldwide for instance to improve thermal properties of polyethylene. Within an European funded project tests were carried out to investigate irradiation effects on natural fibers. Such fibers made out of different PLA grades, biobased PA and PES were treated with electron beam irradiation. Depending on the type of polymer and irradiation dose, Young's modulus were improved by more than 60 %. Beside a detailed view on the trials and results, the talk will also give an introduction to electron beam irradiation, its interaction with polymers and used equipment.