The recent discovery of two types of metallic copper oxide compounds which are superconducting to above 90K has renewed interest in the search for new high temperature superconducting materials. It is significant that both classes of compounds, La2−xSrxCuO4−y and YBa2Cu3O7−δ are intimately related to the extensively studied perovskite family. Both compounds contain highly oxidized, covalently bonded Cu-O sublattices, however, they differ in geometry. In this paper we discuss the relationship of these features to the superconducting properties.