In this paper, we present a monolithic wide tuning range low phase noise voltage-controlled oscillator (VCO) with high output power and high efficiency in 90 nm CMOS process. The proposed VCO is based on a cascode amplifier with a π-feedback network. The propose VCO achieves a maximum output power of 10.6 dBm, and a maximum efficiency of 16.1%, when the dc supply voltage is 2.4 V with a current consumption of 27 mA. The measured phase noise at 1-MHz offset is -104.6 dBc/Hz. The oscillation frequency is from 43.8 to 49.1 GHz. The chip size of the VCO is 514 × 554 μm2. This work has the highest efficiency and the highest output power among all the reported MMW CMOS VCOs without output buffer amplifier.