  We describe possible scenarios of quark deconfinement in compact stars and we
analyze their astrophysical implications. The quark deconfinement process can
proceed rapidly, as a strong deflagration, releasing a huge amount of energy in
a short time and generating an extra neutrino burst. If energy is transferred
efficiently to the surface, like e.g. in the presence of convective
instabilities, this burst could contribute to revitalize a partially failed SN
explosion. We discuss how the neutrino observations from SN1987A would fit in
this scenario. Finally, we focus on the fate of massive and rapidly rotating
progenitors, discussing possible time separations between the moment of the
core collapse and the moment of quark deconfinement. This mechanism can be at
the basis of the interpretation of gamma ray bursts in which lines associated
with heavy elements are present in the spectrum.
