Electrostatic spraying is important in many applications where very fine droplets are desirable. Most electrostatic spraying systems developed to date, however, require that the electrical conductivity of the dispersed fluid is higher than that of the surrounding fluid. This work reports on an experimental investigation of the mechanism for successful electrostatic spraying of a nonconductive fluid into a conductive one. The key role played by the electric stress on the interface between the nonconductive and conductive fluids is evidenced by examining the variations of the emitted drop size, electrical current, and pressure inside the nozzle as functions of the applied voltage, nozzle geometry and distance between the high-voltage nozzle-electrode and the grounded electrode immersed in the surrounding fluid. A comparison of nonconductive-in-conductive and conductive-in-nonconductive spraying systems reveals a difference in behavior that is consistent with the theory of electrohydrodynamics.