Double B perovskite-type series in the system La_0.6Ca_0.4Mn_{1 - x}Me_xO_{3 - δ} with Me{double bond, long}Fe, Co, Ni and x = 0-0.6 were synthesized in air by solid state reactions at 1200 °C from simple oxides and CaCO₃. Almost single phase compositions with small impurities (3-5%) were formed. Replacement of Mn with Me-cations is accompanied by a considerable decrease of electrical conductivity of the prepared ceramics. Lower conductivities of the Me containing compositions compared to La_0.6Ca_0.4MnO_{3 - δ} are explained by stronger polarization of the -Mn^{(α + γ)+}-O^α--Me^{(α - γ)+}-O^α-- fragments of the - O^α--Mn^α+ - O^α--Mn^α+ - O^α--Mn^{(α + γ) +} -O^α--Me^{(α - γ)+}-O^α-- chains in comparison with the -O^α--Mn^α+-O^α--Mn^α+-O^α-- chains without Me-cations, because of different electronegativity of Me and Mn. The double exchange theory gives strong explanation for this phenomenon. Type and level of the electrical conductivity of the La_0.6Ca_0.4Mn_{1 - x}Me_xO_{3 - δ} series are the functions of the [Mn⁴⁺]/[Mn³⁺] and [Me³⁺]/[Me²⁺] ratios. Mn⁴⁺ and Me²⁺-cations are possible point defects which determine the p- and n-type conductivity of compositions, respectively.