Based of known structural frameworks of oxygen-deficient perovskites, an alternate structure for Ba2YCu3O7 is proposed. It is compatible with the X-ray data of that phase. The lattice is made up of perovskite layers of corner-sharing CuO6 octahedra interlinked with corner-sharing square-planar CuO4 units. The proposed structure makes the class of high-Tc superconductors with perovskite-related structures more consistent. © 1987 Springer-Verlag.