LaCuO3 was the first Cu(III) oxide with the perovskite structure. In 1990, J.F. Bringley et al. described the structures of new non-stoichiometric oxides LaCuO3-delta. This paper deals with new materials La(1-x)A(x)CoO(3-delta) (A = Sr, Y) isostructural with the previous oxides. Their preparation conditions, their stability domain and their physical properties are correlated to the nature of the A cation.