The crystallographic, mechanical, thermal and electrical properties of La 0 . 6 AE 0 . 4 MnO 3 perovskites (AE=Ca and Sr) have been investigated. La 0 . 6 Ca 0 . 4 MnO 3 showed an orthorhombic symmetry at room temperature, and its symmetry changed into tetragonal at approximately 500 o C and into cubic at approximately 900 o C. La 0 . 6 Sr 0 . 4 MnO 3 showed tetragonal symmetry at room temperature and its symmetry changed into cubic at temperatures >=90 o C. Transgranular fracture of dense La 0 . 6 AE 0 . 4 MnO 3 specimens, after mechanical strength measurements at temperatures =<400 o C, was indicated, whereas the specimens mechanically tested after the measurement at temperatures >=600 o C showed intergranular fracture. Thermal expansion coefficients (TECs) of the sintered specimens in the temperature range from 50 to 1000 o C were 11.7x10 - 6 / o C for La 0 . 6 Ca 0 . 4 MnO 3 and 12.2x10 - 6 / o C for La 0 . 6 Sr 0 . 4 MnO 3 . Electrical conductivities of the dense specimens at 1000 o C were 227 S/cm for La 0 . 6 Ca 0 . 4 MnO 3 and 213 S/cm for La 0 . 6 Sr 0 . 4 MnO 3 . To synthesize these materials as electric current collectors in high-temperature solid oxide fuel cells (SOFC), La 0 . 6 AE 0 . 4 MnO 3 perovskites were compounded with manganese oxide. The TECs of the composites at around 50 vol.% Mn 3 O 4 were almost the same as that of the Y 2 O 3 stabilized ZrO 2 (YSZ) electrolyte. Electrical conductivities of these dense specimens at 1000 o C were observed to be between 50 and 90 S/cm. Thus, dense La 0 . 6 AE 0 . 4 MnO 3 -Mn 3 O 4 composites are appropriate for the electric current collectors in the SOFC.