The goal of the Thermionic Fuel Element Verification Program (TFEVP) is to demonstrate the technological readiness of a TFE suitable for use as the basic element in a thermionic reactor having an electric power output in the 0.5- to 5-MWe range, and a full-power life of seven years. The TFEVP has made significant progress in developing components capable of withstanding the required neutron fluenee (4x1022 n/cm2, E>0.1 MeV) and the required burnup (5.3%). Technology developed under the TFEVP also supports the 5- to 40-kWe thermionic systems currently of interest to the Strategic Defense Initiative Organization and the Air Force. The fast neutron flux in certain 5- to 40-kWe systems is up to a factor of five less than that in 0.5- to 5MWe systems. Component technology that has been developed for 0.5- to 5-MWe systems will thus be suitable for use in long-life, high-performance, 5- to 40-kWe systems. Components that are being developed by the TFEVP include insulator seals, sheath insulators, fueled emitters, cesium reservoirs, and interconnective TFE components. In addition, the TEEVP has created a preliminary 2-MWe-system design, and is presently evaluating converter performance under various conditions. Prototypic TFEs are also being tested. The TFEVP has encountered and surmounted problems in developing and testing long-life TFEs.