  Wolf-Rayet stars have been detected in a large number of galaxies
experiencing intense bursts of star formation. All stars initially more massive
than a certain, metallicity-dependent, value are believed to experience the
Wolf-Rayet phase at the end of their evolution, just before collapsing in
supernova explosion. The detection of Wolf-Rayet stars puts therefore important
constraints on the evolutionary status of starbursts, the properties of their
Initial Mass Functions and their star formation regime. In this contribution we
review the properties of galaxies hosting Wolf-Rayet stars, with special
emphasis on the factors that determine their presence and evolution, as well as
their impact on the surrounding medium.
