The oxygen permeation fluxes, electrical conductivity and ther mal expansion of LaCo1-xCrxO3 (x = 0.1-0.4) solid solutions have been ascertained to decrease with increasing chromium concentration. The dependence of the oxygen permeability on thickness of the LaCo1-xCrxO3 (x < 0.3) dense ceramic membranes suggests a presence of surface-exchange limitations of the oxygen transport. Introduction of nickel into the cobalt sublattice of LaCo1-xNixO3 has been found to result in a sharp decrease of the oxygen ionic conductivity which is the flux-limiting factor. Electronic conductivity of the solid solutions increases with nickel content. A prolonged stabilization process to attain stationary oxygen flux through LaCo(Cr)O-3 and LaCo(Ni)O-3 membranes has been pointed out. Thermal expansion coefficients of the ceramics have been calculated from the dilatometric data to be in the range (17.3-23.7)X 10(-6) K-1.