Magnetism and transport have been investigated for perovskite cobalt oxides Ln(0.5)Sr(0.5)CoO(3) (Ln = Pr, Nd, Sm and Eu). The crystal structures are monoclinic (P2(1)/n) for Pr0.5Sr0.5CoO3, orthorhombic (Pnma) for Nd0.5Sr0.5CoO3 and Sn0.5Sr0.5CoO3, and cubic (Pm3m) for Eu0.5Sr0.5CoO3. DC magnetization measurements showed ferromagnetic transitions with Curie temperatures (Tc) between 233 and 155 K. Metallic behavior was observed in resistivity-temperature curves below 300 K. This is an entirely different property from that of Ln(0.5)Ba(0.5)CoO(3), which may be qualitatively explained in connection with the crystal structures.