A model on the electronic structure and the superconducting mechanism in the hole-doped cuprates is presented. It is shown that hole doping introduces new bonding and antibonding states near the Fermi level. This drastic change of the electronic structure with hole doping originates basically from the Coulomb repulsions involving the copper 3d 3 z 2− r 2 orbitals. High- T c superconductivity is shown to be mediated by the intersite charge fluctuations between the copper and oxygen atoms, and the transition temperature T c is calculated within the framework of the mean field approximations. The changes of the maximum transition temperature T c,max among the cuprates are also discussed.