It is shown that ion current stabilization for surface ionization mass spectrometers offers many advantages over the conventional methods of regulation which effectively stabilize the sample temperature. A technique is described which allows accurate measurement of very small relative isotopic abundances. A number of problems associated with the design of circuits for emission stabilization of surface ionization sources are considered. A successful stabilizer which maintains the ion current from such a source at a constant value by variation of the source filament temperature is described and the performance when used for the control of potassium positive ion sources is discussed. The stabilizer is capable of reducing ion current drifts, such as those due to exhaustion of the sample, by a factor of 130.