This article reports investigations of insulation failure of needle-plane Saps of micrometric dimensions. Using a piezoelectric translational stage it is possible to set the gap spacing in the range between 0.1 and 40 mu m with a resolution less than 0.04 mu m. The prebreakdown and breakdown characteristics of the needle-plane gap were investigated as a function of the gap spacing, emitter radius, ambient pressure, and conditioning effects. The experimental results showed that the breakdown voltage of a microtip-plane gap is relatively high. For a 2 mu m radius tip set at a 1 mu m gap distance from a planar electrode, the breakdown voltage was about 500 V. It was found that an increase of pressure from 10(-6) to 10(-2) Torr did not influence the value of the threshold voltage for breakdown. de glow discharge conditioning in air at a pressure of similar to 1 Torr increased the value of threshold voltage for breakdown in vacuum by about 20%-30%. The obtained prebreakdown characteristics of microtip type gaps is very important for the development of vacuum microelectronic devices; specifically, these data provide valuable insights to the practical limits to which microtip-gate gaps can be stressed in practical field emitter arrays in field emission displays.