Most previous papers on class E frequency multipliers are based on the assumption that the Q factor of the series-tuned circuit is high enough that the load current is sinusoidal at the harmonic output frequency. It is the purpose of this paper to present a theoretical description of the class E frequency multiplier, in which the assumption of infinite Q is eliminated. Design and performance curves show clearly that the frequency multiplier performances are strongly affected by Q. Also, it is shown that the class E frquency multipliers operating at an efficiency of 100 percent are not realizable for values of Q lower than a minimum Q value