We investigate the reliability of RF switches for high-power, high dynamic range RF applications. Switches in two different CMOS technology platforms (180 nm and 130 nm) were observed to fail catastrophically beyond 33 dBm RF input power. The switches were single-pole double-throw with series-shunt topology. The reliability of a standalone switching series transistor from a single-pole double-throw switch was analyzed to investigate the failure mechanisms involved. Gate dielectric breakdown at high RF input power is demonstrated to lead to the failure of RF switches. Finally, the effect of transistor failure on switch operation is discussed.