Ionic thermocurrent (ITC), ac-conductivity, and electron paramagnetic resonance (EPR) experiments have been performed on solid solutions Pb_1-xRE_xF_2+x. These hetrovalent solid solutions were prepared as crystals and powders by different te chniques. The differences in the dependence on concentration of the electrical properties are explained by the nature of defect structures. Using the ITC method we were able to distinguish different types of dipole defects created by the RE³⁺ cation and the charge compensating interstitial fluoride. The activation energies for all these complexes were determined and correlated with structural aspects. EPR-spectra (0.1 mol% GdF₃ as a probe) for both polycrystalline and single crystals show three different RE-sites and are compared to spectra obtained from other Gd-doped fluorite-structured solid solutions.