The conductivity of the materials LaAlO3, LaGaO3, LaScO3 and LaInO3 all doped with 10% strontium on the A-site and 10% magnesium at the B-site has been measured at different temperatures and oxygen partial pressures. The doped LaGaO3 is found to be an almost pure ionic conductor with a conductivity of 95 mS/cm at 800 degrees C. The conductivity of doped LaGaO3, decreases with time due to precipitation of a secondary phase. The doped LaAlO3 and LaScO3 are mixed conductors in oxidising atmosphere. Their ionic conductivities at 800 degrees C are 1.3 and 0.5 mS/cm, respectively. The conductivities given are total conductivities. The large difference in the conductivities of the investigated materials seems to be caused partly by grain boundary resistance.