This paper reviews the current status of millimeter-wave CMOS power amplifiers. The basic power amplifier architectures will be presented, together with the power combining techniques for higher output power amplifiers. State-of-the-art performances of CMOS power amplifiers, including power gain, output power, and power added efficiency, will be summarized along with various frequencies in millimeter-wave regime. Due to the requirement of modern wireless communication applications for high data rate transmission, the linearity becomes crucial for power amplifier in digital communication systems. Moreover, the efficiency at output power back-off operation is also important, especially for the mobile digital communication devices. The reported linearization techniques in millimeter-wave CMOS power amplifiers will also be presented, with the illustration of design examples.