Preparation and ionic conductivity of the mixed conducting perovskites La1-x,MexCoO3-delta with Me = Sr, Ca were investigated in the composition range x = 0.1-0.5. Two preparation methods, the first via metal complexes in aqueous solution and the second based on a spray-freezing/freeze-drying process, were studied with an emphasis on lower reaction temperatures for the formation of perovskite type oxides. Oxygen ion conductivities were measured as a function of composition x and temperature (550 degrees C-750 degrees C) using oxygen ion conducting microcontacts (made of stabilised zirconia, contact radius in the range 10-80 mu m). Evaluation of the steady-state current voltage curves (slope, curvature) yields the oxygen ion conductivity as a function of the oxygen partial pressure. For all investigated compositions of Sr and Ca substituted perovskites, oxygen transport occurs by a vacancy mechanism. For instance, values of the ionic conductivities are 4.6 x 10(-5) (Omega cm)(-1) for La0.8Sr0.2CoO3-delta and 2.8 x 10(-5) (Omega cm)(-1) for La-0.8, Ca-0.2, CoO3-delta at 700 degrees C in air increasing by nearly a factor of ten with increasing Sr or Ca concentration.