We report on two novel high temperature and potentially highly neutron and gamma radiation resistant electronc technologies that are suitable for nuclear and space applications. The operational effects on these technologies from gamma radiation doses up to 10 megarads and 1‐MeV equivalent neutron fluences up to 1014neutrons/cm2are examined using a calibrated (to appropriate ASTM standards) irradiation chamber in the University of Utah TRIGA Nuclear Reactor. The first high temperature, harsh environment technology is based on microminiature vacuum (MTV) devices. The second high temperature technology is gallium arsenide (GaAs) metal semiconductor field effect transistor (MESFET)‐based devices and circuits that can operate at temperatures up to 350 °C. This MESFET‐based technology also allows a wide range of control with respect to the MESFET’s enhanced resistance to breakdown at elevated temperatures. The MESFET‐based technology has general applicability and works equally well with both enhancement and depletion n‐channel MESFET’s. © 1995American Institute of Physics