Maser emission during post-AGB evolution
  This contribution reviews recent observational results concerning
astronomical masers toward post-AGB objects with a special attention to water
fountain sources and the prototypical source OH231.8+4.2. These sources
represent a short transition phase in the evolution between circumstellar
envelopes around asymptotic giant branch stars and planetary nebulae. The main
masing species are considered and key results are summarized.
