An analysis is given of frequency multiplication with the ideal step-recovery diode in the series-mode of operation. Only one conduction angle per period of the fundamental frequency is allowed. The series resistance of the diode is assumed to be different from zero. General and explicit formulae are given for the input impedance, the output power and the power efficiency. The validity of the approximations is discussed throughout. It is shown that the efficiency, -q, of the power conversion is proportional to 1/n2, and that the maximum value for 17 is about 15% for a times 10 multiplier in this series-mode of operation.