Although the Manley and Rowe relations indicate that complete conversion of fundamental power to any specific harmonic with nonlinear reactance element is possible theoretically, many factors contribute to lowering the efficiency of real multipliers. Analysis, based on a Taylor series expansion of the nonlinear reactance characteristic and Fourier expansion of the voltage and charge, with the introduction of suitable parameters and quiescent conditions, permits the exact determination of the various effects. Given the characteristics of a nonlinear element and the inevitable circuit losses, maximum obtainable efficiency can be predicted from the analysis. Significant increase in efficiency is obtained in Various circuit configurations where undesired harmonics are prevented from being generated er their power is returned to useful output at the desired harmonic frequency. The characteristic of the nonlinear reactance is shown to have a calculable effect on the multiplier efficiency, so that the most desirable characteristic can be specified. Experimental nonlinear capacitance multipliers designed according to the developed theory have provided an efficiency of 50 percent for a quintupler and 70 percent for a tripler, very close to the predicted values.