The transport numbers of electric current carriers in glasses of the PbF_2-2PbO · SiO₂ system are determined by the Tubandt method. It is demonstrated that, in the PbF_2-2PbO · SiO₂ glasses containing up to 20 mol % PbF₂, the electricity transport occurs through protons and fluorine ions. At a content more than 20 mol % PbF₂, the electric current is carried by the fluorine ions. The temperature-concentration dependences of the electric conductivity are studied. The electric conductivity is found to be maximum (σ_100°C = 2 × 10^-8 Ω^-1 cm^-1) at 45-50 mol % PbF₂. The observed dependences logσ =f[PbF₂] and Eσ = f[PbF₂] are interpreted in terms of structural-chemical microinhomogeneity of the glass structure.