The electrical conductivity of Pb1-xRxSnF4+x solid solutions (R = Y, La, Ce, Nd, Sm, Gd), whose lattice is tetragonal and isostructural with beta-PbSnF4, has been studied by F-19 NMR and impedance spectroscopy. The ultimate percentage of cerium group RE fluorides in such solutions is not over 20.0 mol%, and that of gadolinium trifluoride reaches 12.0 mol%. The fluoride anions in the synthesized samples of Pb1-xRxSnF4+x solid solutions occupy, as in beta-PbSnF4, three structurally nonequivalent positions. The charge transfer in complex fluorides of this type at temperatures above 350 K is done by interstitial fluoride ions. At a low substituent concentration (x <= 0.07), the electrical conductivity is almost an order of magnitude lower than that of beta-PbSnF4. The conductivity of the synthesized solid solutions increases with increasing substituent content. The samples containing 10.0-15.0 mol% RF3 have the maximum conductivity. At the same RF3 content, the conductivity of solid solutions, except those containing gadolinium trifluoride, increases with decreasing R3+ radius (from La to Sm).