The effective fragment potential (EFP) method is described and its capabilities illustrated using several applications. The original method, EFP1, was primarily developed to describe aqueous solvation, by representing Coulombic, induction and repulsive interactions via one-electron terms in the ab initio Hamiltonian. It is demonstrated, using water clusters, the Menshutkin reaction and the glycine neutral/zwitterion equilibrium, that agreement with both fully ab initio calculations and experiment are excellent. More recently, the model has been extended so that it can treat any solvent, as well as more difficult links across covalent bonds.