The perovskite-type oxides were synthesized in the series of Ln(1-x)Sr(x)CoO(3) (Ln = Sm, Dy). The formation of solid solutions in Dy1-xSrxCoO3 was limited, compared with that in Sm1-xSrxCoO3. The electrical conductivities of the sintered samples were measured as a function of x in the temperature range 30 to 1000 degrees C. The highest conductivity of around 500 Slcm at 1000 degrees C was found in Sm0.7Sr0.3CoO3. The reactivity of all the samples with YSZ was examined at 800-1000 degrees C for 96 h. The Sr-doped perovskite oxides were more reactive with YSZ and produced SrZrO3 at 900 degrees C after 96 h. However, no reaction product between SmCoO3 and YSZ was observed at 1000 degrees C for 96 h. The cathodic polarization of the oxide electrodes, sputtered on yttria stabilized zirconia (YSZ), was studied at 800-1000 degrees C in air. SmCoO, shows no degradation of the electrode performance at higher temperatures. The thermal expansion measurements on the sintered samples were carried out from room temperature to 1000 degrees C. Large thermal expansion coefficients were found in these samples.