  We have used the Australia Telescope Compact Array (ATCA) to make a sensitive
search for maser emission from the 4765-MHz transition of OH towards a sample
of 55 star formation regions. Maser emission with peak flux densities in excess
of 100 mJy were detected in 14 sites, with 10 of these being new discoveries.
Unlike the ground-state OH transitions the 4765-MHz transition is not predicted
to be circularly polarised and none of the masers observed have detectable
levels of linear, or circular polarisation. Combining our results with those of
previous high resolution observations of other OH transitions we are able to
investigate various theoretical models for the pumping of OH masers.
