Metal-electrolyte interfaces are associated with a strong (approximately 10(8) V m-1) electrostatic field. When such an interface is studied with second harmonic generation, this field can complicate the optical data by introducing a third-order electronic response of the metal. A theoretical framework is presented here for analyzing these dc field-affected second harmonic results for polycrystalline metal electrodes. The macroscopic features of the surface nonlinear polarization are analyzed. It is also shown explicitly that the dc field does not alter the characteristic polarization and angular dependencies of surface second harmonic generation.