Abstract: A gas ionization type vacuum gauge for testing the internal vacuum levels to below 10.sup.-6 torr is disclosed which uses a multipactor discharge means as the source for the electron current used to ionize residual gas molecules. The invention comprises an RF field enhancing cavity which can be constructed of high-vacuum-compatible materials, able to withstand bake-out microwave temperatures and a negatively biased ion collection wave, wire, or grid. A simple ceramic RF feed-through permits simple and noninvasive pressure measurements. The device can be made much smaller than conventional gauges.