HIGH-POWER avalanche-diode oscillators have been reported at X to K-band1.2,3 and also in the UHF frequency range4. This paper will report on pulsed-power outputs of the order of 50 W with an efficiency of over 6 % from specially-profiled silicon avalanche diodes in the 2-8 GHz range. An anomalous mode of UHF oscillation observed at high-bias current levels will also be discussed.