Two methods were used to measure the transference number of a hybrid polymer electrolyte at different salt concentrations. The hybrid polymer electrolyte was based on a radiation induced cross-linked polyether network with propylene carbonate in an interpenetrating liquid phase and LiAsF6 as electrolyte salt. One method for transference number measurements was based on the Hittorf method, which gave values ranging from 0.15 at 0.1 mole kg(-1) to 0.31 at 2.1 mole kg(-1). The other method was the DC-polarization method, which gave values from 0.31 at 0.1 mole kg(-1) to 0.72 at 2.1 mole kg(-1). The difference in the transference numbers between the two methods is explained by contribution from mobile ion-pairs.