  Our view of the high velocity cloud (HVC) system is changing dramatically
with new observations from the Far Ultraviolet Spectroscopic Explorer mission
and the Space Telescope Imaging Spectrograph onboard the Hubble Space
Telescope. In particular, the detection of O VI absorption indicates that many
HVCs have a hot, collisionally-ionized component in addition to the neutral gas
detected in H I 21cm emission. A better understanding of the ionization of this
gas will help to determine the distances of some HVCs, as well as constrain the
properties of a hot Galactic corona or Local Group medium. In this article, I
briefly summarize some recent observations of O VI HVCs.
