The electrical resistivity, , and thermoelectric power of iron phosphate glasses were measured over the temperature range 25°–400°C. The resistivity increased as the iron oxide was replaced by magnesium oxide. The resistivity also varied with the ratio in a glass containing 55% (on mole basis); ρ passed through minimum at a ratio approximately equal to 0.5. From thermoelectric data, the glasses were determined to be p‐type when the ratio was less than 0.38 and n‐type at higher ratios. The results suggest that the carrier mobility is a thermally activated diffusion process similar to that proposed for crystalline transition metal oxides. The conduction activation energy pertains to mobility rather than to the formation of carriers.