We present initial results of a survey correlating structural features of the cuprate superconductors with the occurrence of superconductivity. The best correlation is with the Cu - Cu distance in the plane of the two-dimensional compounds. Superconductivity has been shown only over a narrow region of Cu-Cu separations for both the A2CuO4 and square pyramidal based compounds. On either side of the superconducting region semiconductivity is found for both systems. It is suggested that the key difference between the classes is that oxidation of the A2CuO4 compounds results in removal of anti-bonding electrons, whereas in the square pyramidal compounds these electrons are non-bonding, which allows for greater carrier densities befor chemical instabilities occur. The copper oxide based systems are compared to the bismuth based superconductors. Unsuccessful attempts to synthesize superconductors based on lead are described.