This paper presents the design and experimental results of fully integrated CMOS power sensors for RF built-in self-test (BIST) applications. Using a standard 0.18- m CMOS process, the power sensors, on-chip terminations and switches are integrated with a 5.2GHz variable-gain amplifier. Built-in RF test was performed on the amplifier in the vicinity of 5.2 GHz for demonstration. With the proposed built-in power sensors and BIST technique, the circuit parameters of the amplifier including the forward gain and gain compression were extracted without expensive automatic test equipments while minimum performance degradation of the device under test (DUT) is maintained at multi-gigahertz frequencies.