Field emission from carbon nanotube (CNT) bundles has been applied to develop new class of computational vacuum microelectronics for harsh environment applications. CNTs have demonstrated superior field emission performance because of their low emission threshold, high current density, and are conducive for monolithic integration with silicon structures to develop microelectronic/microsensor systems. In this paper we present high-temperature tolerant "digital" vacuum electronics using CNTs. This technology is applicable to in situ sensor electronics for down-hole applications where the operating environment is high temperature, high pressure, and has corrosive chemicals. The digital and analog electronic devices developed using CNT-vacuum microelectronic technology can be integrated with sensor systems to achieve prolonged stand-alone operation during E&P. NASA-JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles that produce > 15 A/cm2 at applied fields of 6 to 8 V/μm. They have exhibited robust operation in poor vacuums of 10‒7 to 10‒4 Torr-a typically achievable range inside hermetically sealed microcavities. By monolithically integrating CNT cathodes with micromachined Si multi-gate structures we have demonstrated a new class of programmable "vacuum" logic gates. We have achieved switching operation at temperatures up to 700° C. The initial design, operation, and the potential performance in an improved design will be presented in this paper along with vacuum packaging techniques to make stand alone devices for circuit board integration. CNT-vacuum microelectronics opens up a new regime of in situ electronics for novel sensor/electronics systems because of their inherent high-temperature tolerance, and corrosion resistance. Unlike traditional vacuum tubes, these are low power, miniature, and potentially as fast as their solid-state counterparts while exhibiting superior reverse bias or leakage current characteristics. These devices offer potential to significantly enhance E&P operation.