  The minimum and maximum mass of protoneutron stars and neutron stars are
investigated. The hot dense matter is described by relativistic (including
hyperons) and non-relativistic equations of state. We show that the minimum
mass ($\sim$ 0.88 - 1.28 $M_{\sun}$) of a neutron star is determined by the
earliest stage of its evolution and is nearly unaffected by the presence of
hyperons. The maximum mass of a neutron star is limited by the protoneutron
star or hot neutron star stage. Further we find that the delayed collapse of a
neutron star into a black hole during deleptonization is not only possible for
equations of state with softening components, as for instance, hyperons, meson
condensates etc., but also for neutron stars with a pure nucleonic-leptonic
equation of state.
