Aging produced by RF stress is experimentally analyzed on a RF CMOS power amplifier (PA), as a function of the stress power level. The selected circuit topology allows observing individual NMOS and PMOS transistors degradations, as well as the aging effect on the circuit functionality. A direct relation between DC MOSFETs and RF PA (gain) parameters has been observed. NMOS degradation (both in mobility and Vth) is stronger than that of the PMOS. Results suggest that transistors mobility reduction is the main cause of the RF degradation in this circuit.