Samples in the composition series La1-xSrxCoO3 with x = 0-0.8 were synthesized, and their crystal structures, conductivities and catalytic activities were studied. When x < 0.6, they have a rhombohedrally distorted perovskite structure. When x = 0.3-0.5, their conductivities at room temperature are of the order of 10(3) S m(-1). When the temperature is higher than 250 degrees C, the catalytic activities of La1-xSrxCoO3 were very high which reaches a maximum for the sample at x = 0.3. Cylindrical samples were made from La1-xSrxCoO3 x = 0.3 and used as a cathode in sealed CO2 lasers. Compared to the traditional Ag-Cu alloy cathode, the performance of La0.7Sr0.3CoO3 is better. The maximum output of a 1.0 m length laser tube using the new cathode is 53.1 W m(-1).