The effects of ionizing radiation on the operation of polysilicon microelectromechanical systems (MEMS) electrostatic, electrothermal, and bimorph actuators were examined. All devices were irradiated up to a total ionizing dose of 1 megarad(Si) using both a low energy X-ray source (LEXR) and Cobalt-60 (Co-60) gamma source. The electrostatic actuators exhibited a decrease in capacitance and thereby an increase in voltage per deflection when subjected to the LEXR radiation environment. Devices irradiated with the Co-60 source showed no changes in the capacitance/voltage relationship after irradiation. The electrothermal actuator operation was not affected by exposure to either type of ionizing radiation. The tip deflection measurements of the bimorph actuators showed a slight decrease between pre- and post characterization.